<?xml version="1.0" encoding="us-ascii"?>
<!--XBRL document created by RR Donnelley Tagger version 10.0.0.218; Copyright (C) RR Donnelley-->
<!--Based on XBRL 2.1-->
<link:linkbase xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:link="http://www.xbrl.org/2003/linkbase" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#StatementsOfStockholdersEquity" roleURI="http://uspi.com/role/StatementsOfStockholdersEquity" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#BasisOfPresentationDetailsTextual" roleURI="http://uspi.com/role/BasisOfPresentationDetailsTextual" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#InvestmentsInUnconsolidatedAffiliatesAndBusinessCombinationDetails1" roleURI="http://uspi.com/role/InvestmentsInUnconsolidatedAffiliatesAndBusinessCombinationDetails1" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#NoncontrollingInterestsDetails1" roleURI="http://uspi.com/role/NoncontrollingInterestsDetails1" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#LongTermDebtDetailsTextual" roleURI="http://uspi.com/role/LongTermDebtDetailsTextual" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#OtherInvestmentsDetailsTextuals" roleURI="http://uspi.com/role/OtherInvestmentsDetailsTextuals" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#FairValueOfFinancialInstrumentsDetailsTextual" roleURI="http://uspi.com/role/FairValueOfFinancialInstrumentsDetailsTextual" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#EquityDetails" roleURI="http://uspi.com/role/EquityDetails" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#EquityDetails1" roleURI="http://uspi.com/role/EquityDetails1" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#RelatedPartyTransactionsDetailsTextual" roleURI="http://uspi.com/role/RelatedPartyTransactionsDetailsTextual" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#CommitmentsAndContingenciesDetailsTextual" roleURI="http://uspi.com/role/CommitmentsAndContingenciesDetailsTextual" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#FinancialStatementsDetails" roleURI="http://uspi.com/role/FinancialStatementsDetails" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#FinancialStatementsDetails1" roleURI="http://uspi.com/role/FinancialStatementsDetails1" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#FinancialStatementsDetails2" roleURI="http://uspi.com/role/FinancialStatementsDetails2" />
  <link:roleRef xlink:type="simple" xlink:href="uspi-20120930.xsd#FinancialStatementsDetails3" roleURI="http://uspi.com/role/FinancialStatementsDetails3" />
  <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" />
  <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" />
  <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" />
  <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" />
  <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" arcroleURI="http://xbrl.org/int/dim/arcrole/all" />
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/StatementsOfStockholdersEquity" xlink:title="0140 - Statement - Consolidated Statements of Changes in Equity">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementEquityComponentsAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/StatementsOfStockholdersEquity" xlink:title="0140 - Statement - Consolidated Statements of Changes in Equity">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OutstandingStockAwardsMember" xlink:label="us-gaap_OutstandingStockAwardsMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_ParValueMember" xlink:label="uspi_ParValueMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="us-gaap_AdditionalPaidInCapitalMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="us-gaap_RetainedEarningsMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NoncontrollingInterestMember" xlink:label="us-gaap_NoncontrollingInterestMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_OutstandingStockAwardsMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="uspi_ParValueMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AdditionalPaidInCapitalMember" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeMember" order="4" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_RetainedEarningsMember" order="5" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_NoncontrollingInterestMember" order="6" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/StatementsOfStockholdersEquity" xlink:title="0140 - Statement - Consolidated Statements of Changes in Equity">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" order="2" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:StatementLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/StatementsOfStockholdersEquity" xlink:title="0140 - Statement - Consolidated Statements of Changes in Equity">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SharesIssued" xlink:label="us-gaap_SharesIssued" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" xlink:label="us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MinorityInterestDecreaseFromRedemptions" xlink:label="us-gaap_MinorityInterestDecreaseFromRedemptions" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MinorityInterestIncreaseFromStockIssuance" xlink:label="us-gaap_MinorityInterestIncreaseFromStockIssuance" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_ContributionRelatedToEquityAwardGrantsByOther" xlink:label="uspi_ContributionRelatedToEquityAwardGrantsByOther" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StockholdersEquityNoteSpinoffTransaction" xlink:label="us-gaap_StockholdersEquityNoteSpinoffTransaction" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PaymentsOfDividendsCommonStock" xlink:label="us-gaap_PaymentsOfDividendsCommonStock" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NetIncomeIncludingNonControllingInterestNonRedeemable" xlink:label="uspi_NetIncomeIncludingNonControllingInterestNonRedeemable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_SharesIssued" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_MinorityInterestDecreaseFromRedemptions" order="4" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_MinorityInterestIncreaseFromStockIssuance" order="5" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="uspi_ContributionRelatedToEquityAwardGrantsByOther" order="6" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockholdersEquityNoteSpinoffTransaction" order="7" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PaymentsOfDividendsCommonStock" order="8" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="uspi_NetIncomeIncludingNonControllingInterestNonRedeemable" order="9" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTax" order="10" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/StatementsOfStockholdersEquity" xlink:title="0140 - Statement - Consolidated Statements of Changes in Equity">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/BasisOfPresentationDetailsTextual" xlink:title="0601 - Disclosure - Basis of Presentation (Details)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_BasisOfPresentationTable" xlink:label="uspi_BasisOfPresentationTable" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_BasisOfPresentationAxis" xlink:label="uspi_BasisOfPresentationAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="uspi_BasisOfPresentationTable" xlink:to="uspi_BasisOfPresentationAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/BasisOfPresentationDetailsTextual" xlink:title="0601 - Disclosure - Basis of Presentation (Details)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_BasisOfPresentationAxis" xlink:label="uspi_BasisOfPresentationAxis" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_BasisOfPresentationDomain" xlink:label="uspi_BasisOfPresentationDomain" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_ConsolidatedResultsMember" xlink:label="uspi_ConsolidatedResultsMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_EquityMethodMember" xlink:label="uspi_EquityMethodMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_JointOwnershipMember" xlink:label="uspi_JointOwnershipMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_PhysicianOwnersMember" xlink:label="uspi_PhysicianOwnersMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="uspi_BasisOfPresentationAxis" xlink:to="uspi_BasisOfPresentationDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_BasisOfPresentationDomain" xlink:to="uspi_ConsolidatedResultsMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_BasisOfPresentationDomain" xlink:to="uspi_EquityMethodMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_BasisOfPresentationDomain" xlink:to="uspi_JointOwnershipMember" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_BasisOfPresentationDomain" xlink:to="uspi_PhysicianOwnersMember" order="4" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/BasisOfPresentationDetailsTextual" xlink:title="0601 - Disclosure - Basis of Presentation (Details)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_BasisOfPresentationTable" xlink:label="uspi_BasisOfPresentationTable" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_FacilitiesAxis" xlink:label="uspi_FacilitiesAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="uspi_BasisOfPresentationTable" xlink:to="uspi_FacilitiesAxis" order="2" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/BasisOfPresentationDetailsTextual" xlink:title="0601 - Disclosure - Basis of Presentation (Details)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_FacilitiesAxis" xlink:label="uspi_FacilitiesAxis" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_FacilitiesDomain" xlink:label="uspi_FacilitiesDomain" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/country/2012/country-2012-01-31.xsd#country_US" xlink:label="country_US" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/country/2012/country-2012-01-31.xsd#country_GB" xlink:label="country_GB" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_ShortStaySurgicalFacilitiesMember" xlink:label="uspi_ShortStaySurgicalFacilitiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="uspi_FacilitiesAxis" xlink:to="uspi_FacilitiesDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_FacilitiesDomain" xlink:to="country_US" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_FacilitiesDomain" xlink:to="country_GB" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_FacilitiesDomain" xlink:to="uspi_ShortStaySurgicalFacilitiesMember" order="3" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/BasisOfPresentationDetailsTextual" xlink:title="0601 - Disclosure - Basis of Presentation (Details)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_BasisOfPresentationTable" xlink:label="uspi_BasisOfPresentationTable" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_BasisOfPresentationLineItems" xlink:label="uspi_BasisOfPresentationLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="uspi_BasisOfPresentationLineItems" xlink:to="uspi_BasisOfPresentationTable" order="3" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  uspi:BasisOfPresentationLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/BasisOfPresentationDetailsTextual" xlink:title="0601 - Disclosure - Basis of Presentation (Details)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_BasisOfPresentationLineItems" xlink:label="uspi_BasisOfPresentationLineItems" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_BasisOfPresentationTextualAbstract" xlink:label="uspi_BasisOfPresentationTextualAbstract" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NumberOfFacilities" xlink:label="uspi_NumberOfFacilities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_BasisOfPresentationLineItems" xlink:to="uspi_NumberOfFacilities" order="2" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/BasisOfPresentationDetailsTextual" xlink:title="0601 - Disclosure - Basis of Presentation (Details)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_BasisOfPresentationAxis" xlink:label="uspi_BasisOfPresentationAxis" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_BasisOfPresentationDomain" xlink:label="uspi_BasisOfPresentationDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="uspi_BasisOfPresentationAxis" xlink:to="uspi_BasisOfPresentationDomain" order="1" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/BasisOfPresentationDetailsTextual" xlink:title="0601 - Disclosure - Basis of Presentation (Details)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_FacilitiesAxis" xlink:label="uspi_FacilitiesAxis" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_FacilitiesDomain" xlink:label="uspi_FacilitiesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="uspi_FacilitiesAxis" xlink:to="uspi_FacilitiesDomain" order="2" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/InvestmentsInUnconsolidatedAffiliatesAndBusinessCombinationDetails1" xlink:title="06031 - Disclosure - Investments in Unconsolidated Affiliates and Business Combination (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InvestmentHoldingsTable" xlink:label="us-gaap_InvestmentHoldingsTable" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_InvestmentsEffectiveDateAxis" xlink:label="uspi_InvestmentsEffectiveDateAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_InvestmentHoldingsTable" xlink:to="uspi_InvestmentsEffectiveDateAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/InvestmentsInUnconsolidatedAffiliatesAndBusinessCombinationDetails1" xlink:title="06031 - Disclosure - Investments in Unconsolidated Affiliates and Business Combination (Details 1)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_InvestmentsEffectiveDateAxis" xlink:label="uspi_InvestmentsEffectiveDateAxis" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_InvestmentsEffectiveDateDomain" xlink:label="uspi_InvestmentsEffectiveDateDomain" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_EffectiveDateOneMember" xlink:label="uspi_EffectiveDateOneMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_EffectiveDateTwoMember" xlink:label="uspi_EffectiveDateTwoMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_EffectiveDateThreeMember" xlink:label="uspi_EffectiveDateThreeMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_VariousEffectiveDatesMember" xlink:label="uspi_VariousEffectiveDatesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="uspi_InvestmentsEffectiveDateAxis" xlink:to="uspi_InvestmentsEffectiveDateDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_InvestmentsEffectiveDateDomain" xlink:to="uspi_EffectiveDateOneMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_InvestmentsEffectiveDateDomain" xlink:to="uspi_EffectiveDateTwoMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_InvestmentsEffectiveDateDomain" xlink:to="uspi_EffectiveDateThreeMember" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_InvestmentsEffectiveDateDomain" xlink:to="uspi_VariousEffectiveDatesMember" order="4" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/InvestmentsInUnconsolidatedAffiliatesAndBusinessCombinationDetails1" xlink:title="06031 - Disclosure - Investments in Unconsolidated Affiliates and Business Combination (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InvestmentHoldingsTable" xlink:label="us-gaap_InvestmentHoldingsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/invest/2012/invest-2012-01-31.xsd#invest_InvestmentGeographicRegionAxis" xlink:label="invest_InvestmentGeographicRegionAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_InvestmentHoldingsTable" xlink:to="invest_InvestmentGeographicRegionAxis" order="2" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/InvestmentsInUnconsolidatedAffiliatesAndBusinessCombinationDetails1" xlink:title="06031 - Disclosure - Investments in Unconsolidated Affiliates and Business Combination (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/invest/2012/invest-2012-01-31.xsd#invest_InvestmentGeographicRegionAxis" xlink:label="invest_InvestmentGeographicRegionAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/invest/2012/invest-2012-01-31.xsd#invest_InvestmentGeographicRegionDomain" xlink:label="invest_InvestmentGeographicRegionDomain" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_FacilityLocationOneMember" xlink:label="uspi_FacilityLocationOneMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_FacilityLocationTwoMember" xlink:label="uspi_FacilityLocationTwoMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_FacilityLocationThreeMember" xlink:label="uspi_FacilityLocationThreeMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_VariousFacilityLocationMember" xlink:label="uspi_VariousFacilityLocationMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="invest_InvestmentGeographicRegionAxis" xlink:to="invest_InvestmentGeographicRegionDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="invest_InvestmentGeographicRegionDomain" xlink:to="uspi_FacilityLocationOneMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="invest_InvestmentGeographicRegionDomain" xlink:to="uspi_FacilityLocationTwoMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="invest_InvestmentGeographicRegionDomain" xlink:to="uspi_FacilityLocationThreeMember" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="invest_InvestmentGeographicRegionDomain" xlink:to="uspi_VariousFacilityLocationMember" order="4" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/InvestmentsInUnconsolidatedAffiliatesAndBusinessCombinationDetails1" xlink:title="06031 - Disclosure - Investments in Unconsolidated Affiliates and Business Combination (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InvestmentHoldingsTable" xlink:label="us-gaap_InvestmentHoldingsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InvestmentHoldingsLineItems" xlink:label="us-gaap_InvestmentHoldingsLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_InvestmentHoldingsLineItems" xlink:to="us-gaap_InvestmentHoldingsTable" order="3" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:InvestmentHoldingsLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/InvestmentsInUnconsolidatedAffiliatesAndBusinessCombinationDetails1" xlink:title="06031 - Disclosure - Investments in Unconsolidated Affiliates and Business Combination (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InvestmentHoldingsLineItems" xlink:label="us-gaap_InvestmentHoldingsLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliatesAbstract" xlink:label="us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliatesAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates" xlink:label="us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentHoldingsLineItems" xlink:to="us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates" order="2" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/InvestmentsInUnconsolidatedAffiliatesAndBusinessCombinationDetails1" xlink:title="06031 - Disclosure - Investments in Unconsolidated Affiliates and Business Combination (Details 1)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_InvestmentsEffectiveDateAxis" xlink:label="uspi_InvestmentsEffectiveDateAxis" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_InvestmentsEffectiveDateDomain" xlink:label="uspi_InvestmentsEffectiveDateDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="uspi_InvestmentsEffectiveDateAxis" xlink:to="uspi_InvestmentsEffectiveDateDomain" order="1" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/InvestmentsInUnconsolidatedAffiliatesAndBusinessCombinationDetails1" xlink:title="06031 - Disclosure - Investments in Unconsolidated Affiliates and Business Combination (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/invest/2012/invest-2012-01-31.xsd#invest_InvestmentGeographicRegionAxis" xlink:label="invest_InvestmentGeographicRegionAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/invest/2012/invest-2012-01-31.xsd#invest_InvestmentGeographicRegionDomain" xlink:label="invest_InvestmentGeographicRegionDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="invest_InvestmentGeographicRegionAxis" xlink:to="invest_InvestmentGeographicRegionDomain" order="2" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/NoncontrollingInterestsDetails1" xlink:title="06041 - Disclosure - Noncontrolling Interests (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestByLegalEntityTable" xlink:label="us-gaap_RedeemableNoncontrollingInterestByLegalEntityTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_RedeemableNoncontrollingInterestByLegalEntityTable" xlink:to="us-gaap_StatementEquityComponentsAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/NoncontrollingInterestsDetails1" xlink:title="06041 - Disclosure - Noncontrolling Interests (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_RedeemableNoncontrollingInterestsMember" xlink:label="uspi_RedeemableNoncontrollingInterestsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="uspi_RedeemableNoncontrollingInterestsMember" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/NoncontrollingInterestsDetails1" xlink:title="06041 - Disclosure - Noncontrolling Interests (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestByLegalEntityTable" xlink:label="us-gaap_RedeemableNoncontrollingInterestByLegalEntityTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestLineItems" xlink:label="us-gaap_RedeemableNoncontrollingInterestLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_RedeemableNoncontrollingInterestLineItems" xlink:to="us-gaap_RedeemableNoncontrollingInterestByLegalEntityTable" order="2" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:RedeemableNoncontrollingInterestLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/NoncontrollingInterestsDetails1" xlink:title="06041 - Disclosure - Noncontrolling Interests (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestLineItems" xlink:label="us-gaap_RedeemableNoncontrollingInterestLineItems" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NoncontrollingInterestsRedeemableAbstract" xlink:label="uspi_NoncontrollingInterestsRedeemableAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToNoncontrollingInterest" xlink:label="us-gaap_TemporaryEquityCarryingAmountAttributableToNoncontrollingInterest" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest" xlink:label="us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" xlink:label="us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MinorityInterestDecreaseFromRedemptions" xlink:label="us-gaap_MinorityInterestDecreaseFromRedemptions" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MinorityInterestIncreaseFromStockIssuance" xlink:label="us-gaap_MinorityInterestIncreaseFromStockIssuance" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation" xlink:label="us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RedeemableNoncontrollingInterestLineItems" xlink:to="us-gaap_TemporaryEquityCarryingAmountAttributableToNoncontrollingInterest" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RedeemableNoncontrollingInterestLineItems" xlink:to="us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RedeemableNoncontrollingInterestLineItems" xlink:to="us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" order="4" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RedeemableNoncontrollingInterestLineItems" xlink:to="us-gaap_MinorityInterestDecreaseFromRedemptions" order="5" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RedeemableNoncontrollingInterestLineItems" xlink:to="us-gaap_MinorityInterestIncreaseFromStockIssuance" order="6" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RedeemableNoncontrollingInterestLineItems" xlink:to="us-gaap_NoncontrollingInterestDecreaseFromDeconsolidation" order="7" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/NoncontrollingInterestsDetails1" xlink:title="06041 - Disclosure - Noncontrolling Interests (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_CreditFacilityAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NonExtendedTermLoansMember" xlink:label="uspi_NonExtendedTermLoansMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_ExtendedTermLoansMember" xlink:label="uspi_ExtendedTermLoansMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NewTermLoansMember" xlink:label="uspi_NewTermLoansMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="us-gaap_RevolvingCreditFacilityMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LetterOfCreditMember" xlink:label="us-gaap_LetterOfCreditMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="uspi_NonExtendedTermLoansMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="uspi_ExtendedTermLoansMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="uspi_NewTermLoansMember" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_RevolvingCreditFacilityMember" order="4" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_LetterOfCreditMember" order="5" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RangeAxis" xlink:label="us-gaap_RangeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_RangeAxis" order="2" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RangeAxis" xlink:label="us-gaap_RangeAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RangeMember" xlink:label="us-gaap_RangeMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MinimumMember" xlink:label="us-gaap_MinimumMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MaximumMember" xlink:label="us-gaap_MaximumMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RangeAxis" xlink:to="us-gaap_RangeMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MinimumMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RangeMember" xlink:to="us-gaap_MaximumMember" order="2" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentAxis" order="3" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_EightPointEightSevenFivePercentageSeniorSubordinatedNotesMember" xlink:label="uspi_EightPointEightSevenFivePercentageSeniorSubordinatedNotesMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_ZeroPointNineTwoFiveSeniorSubordinatedToggleNotesMember" xlink:label="uspi_ZeroPointNineTwoFiveSeniorSubordinatedToggleNotesMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NinePointZeroPercentageSeniorNotesDueTwoThousandTwentyMember" xlink:label="uspi_NinePointZeroPercentageSeniorNotesDueTwoThousandTwentyMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="uspi_EightPointEightSevenFivePercentageSeniorSubordinatedNotesMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="uspi_ZeroPointNineTwoFiveSeniorSubordinatedToggleNotesMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="uspi_NinePointZeroPercentageSeniorNotesDueTwoThousandTwentyMember" order="3" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_RatioAxis" xlink:label="uspi_RatioAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="uspi_RatioAxis" order="4" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_RatioAxis" xlink:label="uspi_RatioAxis" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_RatioDomain" xlink:label="uspi_RatioDomain" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NumeratorMember" xlink:label="uspi_NumeratorMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_DenominatorMember" xlink:label="uspi_DenominatorMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="uspi_RatioAxis" xlink:to="uspi_RatioDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_RatioDomain" xlink:to="uspi_NumeratorMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="uspi_RatioDomain" xlink:to="uspi_DenominatorMember" order="2" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentTable" order="5" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:DebtInstrumentLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_LongTermDebtTextualAbstract" xlink:label="uspi_LongTermDebtTextualAbstract" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_MaximumValueOfNewDebtArrangement" xlink:label="uspi_MaximumValueOfNewDebtArrangement" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SecuredDebt" xlink:label="us-gaap_SecuredDebt" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LineOfCreditFacilityExpirationDate1" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RepaymentsOfLongTermLinesOfCredit" xlink:label="us-gaap_RepaymentsOfLongTermLinesOfCredit" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_CreditFacilityPercentageOfPeriodicPrincipalPayment" xlink:label="uspi_CreditFacilityPercentageOfPeriodicPrincipalPayment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_LineOfCreditFacilityParticipationFeePercentage" xlink:label="uspi_LineOfCreditFacilityParticipationFeePercentage" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SeniorNotes" xlink:label="us-gaap_SeniorNotes" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SubordinatedDebt" xlink:label="us-gaap_SubordinatedDebt" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentMaturityDate" xlink:label="us-gaap_DebtInstrumentMaturityDate" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LineOfCreditFacilityDateOfFirstRequiredPayment1" xlink:label="us-gaap_LineOfCreditFacilityDateOfFirstRequiredPayment1" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LineOfCreditFacilityAmountOutstanding" xlink:label="us-gaap_LineOfCreditFacilityAmountOutstanding" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="uspi_MaximumValueOfNewDebtArrangement" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_SecuredDebt" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" order="4" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityExpirationDate1" order="5" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_RepaymentsOfLongTermLinesOfCredit" order="6" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="uspi_CreditFacilityPercentageOfPeriodicPrincipalPayment" order="7" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentBasisSpreadOnVariableRate" order="8" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" order="9" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="uspi_LineOfCreditFacilityParticipationFeePercentage" order="10" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_SeniorNotes" order="11" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_SubordinatedDebt" order="12" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage" order="13" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentMaturityDate" order="14" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityDateOfFirstRequiredPayment1" order="15" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" order="16" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityAmountOutstanding" order="17" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityDomain" order="1" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RangeAxis" xlink:label="us-gaap_RangeAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RangeMember" xlink:label="us-gaap_RangeMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RangeAxis" xlink:to="us-gaap_RangeMember" order="2" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" order="3" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/LongTermDebtDetailsTextual" xlink:title="0605 - Disclosure - Long-term Debt (Details)">
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_RatioAxis" xlink:label="uspi_RatioAxis" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_RatioDomain" xlink:label="uspi_RatioDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="uspi_RatioAxis" xlink:to="uspi_RatioDomain" order="4" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/OtherInvestmentsDetailsTextuals" xlink:title="0606 - Disclosure - Other Investments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable" xlink:label="us-gaap_ScheduleOfVariableInterestEntitiesTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" xlink:label="us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfVariableInterestEntitiesTable" xlink:to="us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/OtherInvestmentsDetailsTextuals" xlink:title="0606 - Disclosure - Other Investments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" xlink:label="us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:label="us-gaap_ClassificationOfVariableInterestEntityDomain" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember" xlink:label="us-gaap_VariableInterestEntityPrimaryBeneficiaryMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" xlink:to="us-gaap_ClassificationOfVariableInterestEntityDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:to="us-gaap_VariableInterestEntityPrimaryBeneficiaryMember" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/OtherInvestmentsDetailsTextuals" xlink:title="0606 - Disclosure - Other Investments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable" xlink:label="us-gaap_ScheduleOfVariableInterestEntitiesTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_VariableInterestEntityLineItems" xlink:label="us-gaap_VariableInterestEntityLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_VariableInterestEntityLineItems" xlink:to="us-gaap_ScheduleOfVariableInterestEntitiesTable" order="2" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:VariableInterestEntityLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/OtherInvestmentsDetailsTextuals" xlink:title="0606 - Disclosure - Other Investments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_VariableInterestEntityLineItems" xlink:label="us-gaap_VariableInterestEntityLineItems" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_OtherInvestmentsTextualAbstract" xlink:label="uspi_OtherInvestmentsTextualAbstract" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NumberOfSubsidiariesForConsolidation" xlink:label="uspi_NumberOfSubsidiariesForConsolidation" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NumberOfSurgicalFacilitiesOperatesAndManages" xlink:label="uspi_NumberOfSurgicalFacilitiesOperatesAndManages" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssets" xlink:label="us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssets" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_VariableInterestEntityConsolidatedCarryingAmountLiabilities" xlink:label="us-gaap_VariableInterestEntityConsolidatedCarryingAmountLiabilities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableInterestEntityLineItems" xlink:to="uspi_NumberOfSubsidiariesForConsolidation" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableInterestEntityLineItems" xlink:to="uspi_NumberOfSurgicalFacilitiesOperatesAndManages" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableInterestEntityLineItems" xlink:to="us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssets" order="4" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableInterestEntityLineItems" xlink:to="us-gaap_VariableInterestEntityConsolidatedCarryingAmountLiabilities" order="5" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/OtherInvestmentsDetailsTextuals" xlink:title="0606 - Disclosure - Other Investments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" xlink:label="us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:label="us-gaap_ClassificationOfVariableInterestEntityDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" xlink:to="us-gaap_ClassificationOfVariableInterestEntityDomain" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FairValueOfFinancialInstrumentsDetailsTextual" xlink:title="0608 - Disclosure - Fair Value of Financial Instruments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueByMeasurementFrequencyAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FairValueOfFinancialInstrumentsDetailsTextual" xlink:title="0608 - Disclosure - Fair Value of Financial Instruments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="us-gaap_FairValueInputsLevel2Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByMeasurementFrequencyAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel2Member" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FairValueOfFinancialInstrumentsDetailsTextual" xlink:title="0608 - Disclosure - Fair Value of Financial Instruments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="us-gaap_BalanceSheetLocationAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_BalanceSheetLocationAxis" order="2" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FairValueOfFinancialInstrumentsDetailsTextual" xlink:title="0608 - Disclosure - Fair Value of Financial Instruments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="us-gaap_BalanceSheetLocationAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="us-gaap_BalanceSheetLocationDomain" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherCurrentAssetsMember" xlink:label="us-gaap_OtherCurrentAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_BalanceSheetLocationAxis" xlink:to="us-gaap_BalanceSheetLocationDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_BalanceSheetLocationDomain" xlink:to="us-gaap_OtherCurrentAssetsMember" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FairValueOfFinancialInstrumentsDetailsTextual" xlink:title="0608 - Disclosure - Fair Value of Financial Instruments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" order="3" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FairValueOfFinancialInstrumentsDetailsTextual" xlink:title="0608 - Disclosure - Fair Value of Financial Instruments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_FairValueOfFinancialInstrumentsTextualAbstract" xlink:label="uspi_FairValueOfFinancialInstrumentsTextualAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AvailableForSaleSecuritiesFairValueDisclosure" xlink:label="us-gaap_AvailableForSaleSecuritiesFairValueDisclosure" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesFairValueDisclosure" order="2" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FairValueOfFinancialInstrumentsDetailsTextual" xlink:title="0608 - Disclosure - Fair Value of Financial Instruments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FairValueByMeasurementFrequencyAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" order="1" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FairValueOfFinancialInstrumentsDetailsTextual" xlink:title="0608 - Disclosure - Fair Value of Financial Instruments (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="us-gaap_BalanceSheetLocationAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="us-gaap_BalanceSheetLocationDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_BalanceSheetLocationAxis" xlink:to="us-gaap_BalanceSheetLocationDomain" order="2" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/EquityDetails" xlink:title="0609 - Disclosure - Equity (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/EquityDetails" xlink:title="0609 - Disclosure - Equity (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsReportLineDomain" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsReportLineDomain" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_SalariesBenefitAndOtherEmployeeCostsMember" xlink:label="uspi_SalariesBenefitAndOtherEmployeeCostsMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherOperatingExpenseMember" xlink:label="us-gaap_OtherOperatingExpenseMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsReportLineDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsReportLineDomain" xlink:to="uspi_SalariesBenefitAndOtherEmployeeCostsMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsReportLineDomain" xlink:to="us-gaap_GeneralAndAdministrativeExpenseMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsReportLineDomain" xlink:to="us-gaap_OtherOperatingExpenseMember" order="3" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/EquityDetails" xlink:title="0609 - Disclosure - Equity (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" order="2" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/EquityDetails" xlink:title="0609 - Disclosure - Equity (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract" xlink:label="us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax" xlink:label="us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax" order="4" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/EquityDetails" xlink:title="0609 - Disclosure - Equity (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsReportLineDomain" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsReportLineDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsByReportLineAxis" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsReportLineDomain" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/EquityDetails1" xlink:title="06091 - Disclosure - Equity (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:to="us-gaap_AwardTypeAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/EquityDetails1" xlink:title="06091 - Disclosure - Equity (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_ShareAwardsMember" xlink:label="uspi_ShareAwardsMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="us-gaap_EmployeeStockOptionMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_WarrantMember" xlink:label="us-gaap_WarrantMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="uspi_ShareAwardsMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_EmployeeStockOptionMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_WarrantMember" order="3" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/EquityDetails1" xlink:title="06091 - Disclosure - Equity (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" order="2" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/EquityDetails1" xlink:title="06091 - Disclosure - Equity (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract" xlink:label="us-gaap_ShareBasedCompensationAllocationAndClassificationInFinancialStatementsAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax" xlink:label="us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax" order="4" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/EquityDetails1" xlink:title="06091 - Disclosure - Equity (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/RelatedPartyTransactionsDetailsTextual" xlink:title="0610 - Disclosure - Related Party Transactions (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="us-gaap_BalanceSheetLocationAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_BalanceSheetLocationAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/RelatedPartyTransactionsDetailsTextual" xlink:title="0610 - Disclosure - Related Party Transactions (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="us-gaap_BalanceSheetLocationAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="us-gaap_BalanceSheetLocationDomain" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_OtherCurrentLiabilitiesMember" xlink:label="uspi_OtherCurrentLiabilitiesMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_OtherLongTermLiabilitiesMember" xlink:label="uspi_OtherLongTermLiabilitiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_BalanceSheetLocationAxis" xlink:to="us-gaap_BalanceSheetLocationDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_BalanceSheetLocationDomain" xlink:to="uspi_OtherCurrentLiabilitiesMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_BalanceSheetLocationDomain" xlink:to="uspi_OtherLongTermLiabilitiesMember" order="2" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/RelatedPartyTransactionsDetailsTextual" xlink:title="0610 - Disclosure - Related Party Transactions (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="us-gaap_RelatedPartyTransactionLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" order="2" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:RelatedPartyTransactionLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/RelatedPartyTransactionsDetailsTextual" xlink:title="0610 - Disclosure - Related Party Transactions (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="us-gaap_RelatedPartyTransactionLineItems" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_RelatedPartyTransactionsTextualAbstract" xlink:label="uspi_RelatedPartyTransactionsTextualAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ManagementFeePayable" xlink:label="us-gaap_ManagementFeePayable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_ManagementFeePayable" order="2" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/RelatedPartyTransactionsDetailsTextual" xlink:title="0610 - Disclosure - Related Party Transactions (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="us-gaap_BalanceSheetLocationAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="us-gaap_BalanceSheetLocationDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_BalanceSheetLocationAxis" xlink:to="us-gaap_BalanceSheetLocationDomain" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/CommitmentsAndContingenciesDetailsTextual" xlink:title="0611 - Disclosure - Commitments and Contingencies (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfGuaranteeObligationsTable" xlink:label="us-gaap_ScheduleOfGuaranteeObligationsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfGuaranteeObligationsTable" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/CommitmentsAndContingenciesDetailsTextual" xlink:title="0611 - Disclosure - Commitments and Contingencies (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SubsidiaryOfCommonParentMember" xlink:label="us-gaap_SubsidiaryOfCommonParentMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MajorityOwnedSubsidiaryUnconsolidatedMember" xlink:label="us-gaap_MajorityOwnedSubsidiaryUnconsolidatedMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NonAffiliatedEntityMember" xlink:label="uspi_NonAffiliatedEntityMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_ObligationOfSaleOfFacilitiesMember" xlink:label="uspi_ObligationOfSaleOfFacilitiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="us-gaap_SubsidiaryOfCommonParentMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="us-gaap_MajorityOwnedSubsidiaryUnconsolidatedMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="uspi_NonAffiliatedEntityMember" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="uspi_ObligationOfSaleOfFacilitiesMember" order="4" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/CommitmentsAndContingenciesDetailsTextual" xlink:title="0611 - Disclosure - Commitments and Contingencies (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfGuaranteeObligationsTable" xlink:label="us-gaap_ScheduleOfGuaranteeObligationsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_GuaranteeObligationsLineItems" xlink:label="us-gaap_GuaranteeObligationsLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_GuaranteeObligationsLineItems" xlink:to="us-gaap_ScheduleOfGuaranteeObligationsTable" order="2" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:GuaranteeObligationsLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/CommitmentsAndContingenciesDetailsTextual" xlink:title="0611 - Disclosure - Commitments and Contingencies (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_GuaranteeObligationsLineItems" xlink:label="us-gaap_GuaranteeObligationsLineItems" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_CommitmentsAndContingenciesTextualAbstract" xlink:label="uspi_CommitmentsAndContingenciesTextualAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_GuaranteeObligationsMaximumExposure" xlink:label="us-gaap_GuaranteeObligationsMaximumExposure" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_GuaranteeObligationsCurrentCarryingValue" xlink:label="us-gaap_GuaranteeObligationsCurrentCarryingValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GuaranteeObligationsLineItems" xlink:to="us-gaap_GuaranteeObligationsMaximumExposure" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_GuaranteeObligationsLineItems" xlink:to="us-gaap_GuaranteeObligationsCurrentCarryingValue" order="3" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/CommitmentsAndContingenciesDetailsTextual" xlink:title="0611 - Disclosure - Commitments and Contingencies (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails" xlink:title="0613 - Disclosure - Condensed Consolidating Financial Statements (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:label="us-gaap_ScheduleOfCondensedFinancialStatementsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:to="dei_LegalEntityAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails" xlink:title="0613 - Disclosure - Condensed Consolidating Financial Statements (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_GuarantorSubsidiariesMember" xlink:label="us-gaap_GuarantorSubsidiariesMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NonParticipatingInvesteesMember" xlink:label="uspi_NonParticipatingInvesteesMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ConsolidationEliminationsMember" xlink:label="us-gaap_ConsolidationEliminationsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="us-gaap_GuarantorSubsidiariesMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="uspi_NonParticipatingInvesteesMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="us-gaap_ConsolidationEliminationsMember" order="3" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails" xlink:title="0613 - Disclosure - Condensed Consolidating Financial Statements (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:label="us-gaap_ScheduleOfCondensedFinancialStatementsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:label="us-gaap_CondensedFinancialStatementsCaptionsLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_ScheduleOfCondensedFinancialStatementsTable" order="2" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:CondensedFinancialStatementsCaptionsLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails" xlink:title="0613 - Disclosure - Condensed Consolidating Financial Statements (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:label="us-gaap_CondensedFinancialStatementsCaptionsLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="us-gaap_StatementOfFinancialPositionAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="us-gaap_AssetsAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AssetsCurrentAbstract" xlink:label="us-gaap_AssetsCurrentAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AvailableForSaleSecuritiesCurrent" xlink:label="us-gaap_AvailableForSaleSecuritiesCurrent" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:label="us-gaap_AccountsReceivableNetCurrent" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherReceivablesNetCurrent" xlink:label="us-gaap_OtherReceivablesNetCurrent" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InventoryNet" xlink:label="us-gaap_InventoryNet" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="us-gaap_AssetsCurrent" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="us-gaap_PropertyPlantAndEquipmentNet" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_EquityMethodInvestments" xlink:label="us-gaap_EquityMethodInvestments" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IntangibleAssetsNetIncludingGoodwill" xlink:label="us-gaap_IntangibleAssetsNetIncludingGoodwill" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="us-gaap_OtherAssetsNoncurrent" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="us-gaap_LiabilitiesCurrentAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="us-gaap_AccountsPayableCurrent" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AccruedLiabilitiesAndOtherLiabilities" xlink:label="us-gaap_AccruedLiabilitiesAndOtherLiabilities" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LongTermDebtCurrent" xlink:label="us-gaap_LongTermDebtCurrent" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="us-gaap_LiabilitiesCurrent" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LongTermDebtNoncurrent" xlink:label="us-gaap_LongTermDebtNoncurrent" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="us-gaap_OtherLiabilitiesNoncurrent" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_MinorityInterest" xlink:label="us-gaap_MinorityInterest" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" order="4" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesCurrent" order="5" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_AccountsReceivableNetCurrent" order="6" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_OtherReceivablesNetCurrent" order="7" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_InventoryNet" order="8" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_PrepaidExpenseAndOtherAssetsCurrent" order="9" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_AssetsCurrent" order="10" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_PropertyPlantAndEquipmentNet" order="11" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_EquityMethodInvestments" order="12" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_IntangibleAssetsNetIncludingGoodwill" order="13" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_OtherAssetsNoncurrent" order="14" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_Assets" order="15" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_AccountsPayableCurrent" order="18" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_AccruedLiabilitiesAndOtherLiabilities" order="19" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_LongTermDebtCurrent" order="20" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_LiabilitiesCurrent" order="21" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_LongTermDebtNoncurrent" order="22" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_OtherLiabilitiesNoncurrent" order="23" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_StockholdersEquity" order="24" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_MinorityInterest" order="25" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity" order="26" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails" xlink:title="0613 - Disclosure - Condensed Consolidating Financial Statements (Details)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails1" xlink:title="06131 - Disclosure - Condensed Consolidating Financial Statements (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:label="us-gaap_ScheduleOfCondensedFinancialStatementsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:to="dei_LegalEntityAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails1" xlink:title="06131 - Disclosure - Condensed Consolidating Financial Statements (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_GuarantorSubsidiariesMember" xlink:label="us-gaap_GuarantorSubsidiariesMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NonParticipatingInvesteesMember" xlink:label="uspi_NonParticipatingInvesteesMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ConsolidationEliminationsMember" xlink:label="us-gaap_ConsolidationEliminationsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="us-gaap_GuarantorSubsidiariesMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="uspi_NonParticipatingInvesteesMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="us-gaap_ConsolidationEliminationsMember" order="3" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails1" xlink:title="06131 - Disclosure - Condensed Consolidating Financial Statements (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:label="us-gaap_ScheduleOfCondensedFinancialStatementsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:label="us-gaap_CondensedFinancialStatementsCaptionsLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_ScheduleOfCondensedFinancialStatementsTable" order="2" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:CondensedFinancialStatementsCaptionsLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails1" xlink:title="06131 - Disclosure - Condensed Consolidating Financial Statements (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:label="us-gaap_CondensedFinancialStatementsCaptionsLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncomeStatementAbstract" xlink:label="us-gaap_IncomeStatementAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_SalesRevenueServicesNet" xlink:label="us-gaap_SalesRevenueServicesNet" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments" xlink:label="us-gaap_IncomeLossFromEquityMethodInvestments" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_OperatingExpensesExcludingDepreciationAndAmortization" xlink:label="uspi_OperatingExpensesExcludingDepreciationAndAmortization" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="us-gaap_DepreciationDepletionAndAmortization" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="us-gaap_OperatingIncomeLoss" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_InterestExpense" xlink:label="us-gaap_InterestExpense" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="us-gaap_OtherNonoperatingIncomeExpense" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="us-gaap_IncomeTaxExpenseBenefit" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" xlink:label="us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" xlink:label="us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="us-gaap_NetIncomeLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_SalesRevenueServicesNet" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_IncomeLossFromEquityMethodInvestments" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="uspi_OperatingExpensesExcludingDepreciationAndAmortization" order="4" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_DepreciationDepletionAndAmortization" order="5" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_OperatingIncomeLoss" order="6" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_InterestExpense" order="7" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_GainsLossesOnExtinguishmentOfDebt" order="8" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_OtherNonoperatingIncomeExpense" order="9" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" order="10" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_IncomeTaxExpenseBenefit" order="11" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" order="12" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" order="13" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_ProfitLoss" order="14" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" order="15" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_NetIncomeLoss" order="16" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails1" xlink:title="06131 - Disclosure - Condensed Consolidating Financial Statements (Details 1)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails2" xlink:title="06132 - Disclosure - Condensed Consolidating Financial Statements (Details 2)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:label="us-gaap_ScheduleOfCondensedFinancialStatementsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:to="dei_LegalEntityAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails2" xlink:title="06132 - Disclosure - Condensed Consolidating Financial Statements (Details 2)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_GuarantorSubsidiariesMember" xlink:label="us-gaap_GuarantorSubsidiariesMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NonParticipatingInvesteesMember" xlink:label="uspi_NonParticipatingInvesteesMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ConsolidationEliminationsMember" xlink:label="us-gaap_ConsolidationEliminationsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="us-gaap_GuarantorSubsidiariesMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="uspi_NonParticipatingInvesteesMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="us-gaap_ConsolidationEliminationsMember" order="3" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails2" xlink:title="06132 - Disclosure - Condensed Consolidating Financial Statements (Details 2)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:label="us-gaap_ScheduleOfCondensedFinancialStatementsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:label="us-gaap_CondensedFinancialStatementsCaptionsLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_ScheduleOfCondensedFinancialStatementsTable" order="2" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:CondensedFinancialStatementsCaptionsLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails2" xlink:title="06132 - Disclosure - Condensed Consolidating Financial Statements (Details 2)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:label="us-gaap_CondensedFinancialStatementsCaptionsLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract" xlink:label="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossTaxAbstract" xlink:label="us-gaap_OtherComprehensiveIncomeLossTaxAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_AvailableForSaleSecuritiesChangeInNetUnrealizedHoldingGainLossNetOfTax" xlink:label="us-gaap_AvailableForSaleSecuritiesChangeInNetUnrealizedHoldingGainLossNetOfTax" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_OtherComprehensiveIncomeUnrealizedGainLossOnForeignCurrencyContractNetOfTax" xlink:label="uspi_OtherComprehensiveIncomeUnrealizedGainLossOnForeignCurrencyContractNetOfTax" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_ReclassificationsDueToSpinOffOfForeignSubsidiariesAbstract" xlink:label="uspi_ReclassificationsDueToSpinOffOfForeignSubsidiariesAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentRealizedUponSaleOrLiquidationNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentRealizedUponSaleOrLiquidationNetOfTax" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTax" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_ComprehensiveIncomeLossesNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:label="uspi_ComprehensiveIncomeLossesNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_ProfitLoss" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" order="4" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesChangeInNetUnrealizedHoldingGainLossNetOfTax" order="5" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="uspi_OtherComprehensiveIncomeUnrealizedGainLossOnForeignCurrencyContractNetOfTax" order="6" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax" order="7" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentRealizedUponSaleOrLiquidationNetOfTax" order="9" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTax" order="10" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_ComprehensiveIncomeNetOfTax" order="11" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest" order="12" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="uspi_ComprehensiveIncomeLossesNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" order="13" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails2" xlink:title="06132 - Disclosure - Condensed Consolidating Financial Statements (Details 2)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="1" />
  </link:definitionLink>
  <!-- Hypercube Definition (Line Items to Hypercube)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails3" xlink:title="06133 - Disclosure - Condensed Consolidating Financial Statements (Details 3)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:label="us-gaap_ScheduleOfCondensedFinancialStatementsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:to="dei_LegalEntityAxis" order="1" />
  </link:definitionLink>
  <!-- Domain Members -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails3" xlink:title="06133 - Disclosure - Condensed Consolidating Financial Statements (Details 3)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_GuarantorSubsidiariesMember" xlink:label="us-gaap_GuarantorSubsidiariesMember" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_NonParticipatingInvesteesMember" xlink:label="uspi_NonParticipatingInvesteesMember" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ConsolidationEliminationsMember" xlink:label="us-gaap_ConsolidationEliminationsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="us-gaap_GuarantorSubsidiariesMember" order="1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="uspi_NonParticipatingInvesteesMember" order="2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="dei_EntityDomain" xlink:to="us-gaap_ConsolidationEliminationsMember" order="3" />
  </link:definitionLink>
  <!-- Hypercube Definition (All)-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails3" xlink:title="06133 - Disclosure - Condensed Consolidating Financial Statements (Details 3)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ScheduleOfCondensedFinancialStatementsTable" xlink:label="us-gaap_ScheduleOfCondensedFinancialStatementsTable" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:label="us-gaap_CondensedFinancialStatementsCaptionsLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_ScheduleOfCondensedFinancialStatementsTable" order="2" xbrldt:closed="true" xbrldt:contextElement="segment" />
  </link:definitionLink>
  <!-- Inheritance for Line Items:  us-gaap:CondensedFinancialStatementsCaptionsLineItems-->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails3" xlink:title="06133 - Disclosure - Condensed Consolidating Financial Statements (Details 3)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:label="us-gaap_CondensedFinancialStatementsCaptionsLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_StatementOfCashFlowsAbstract" xlink:label="us-gaap_StatementOfCashFlowsAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" xlink:label="us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_LossOnEarlyRetirementOfDebt" xlink:label="uspi_LossOnEarlyRetirementOfDebt" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_ChangesInOperatingAndRelatedPartiesAssetsAndLiabilitiesAndNoncashItemsIncludedInNetIncomeLoss" xlink:label="uspi_ChangesInOperatingAndRelatedPartiesAssetsAndLiabilitiesAndNoncashItemsIncludedInNetIncomeLoss" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_PurchasesAndSalesOfNewBusinessesAndEquityInterestsNet" xlink:label="uspi_PurchasesAndSalesOfNewBusinessesAndEquityInterestsNet" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities" xlink:label="us-gaap_PaymentsForProceedsFromOtherInvestingActivities" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt" xlink:label="us-gaap_ProceedsFromIssuanceOfLongTermDebt" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_ProceedsFromPaymentsToMinorityShareholders" xlink:label="us-gaap_ProceedsFromPaymentsToMinorityShareholders" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PaymentsOfDividendsMinorityInterest" xlink:label="us-gaap_PaymentsOfDividendsMinorityInterest" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_PaymentsOfDividendsCommonStock" xlink:label="us-gaap_PaymentsOfDividendsCommonStock" />
    <link:loc xlink:type="locator" xlink:href="uspi-20120930.xsd#uspi_DecreaseIncreaseInCashHeldOnBehalfOfUnconsolidatedAffiliates" xlink:label="uspi_DecreaseIncreaseInCashHeldOnBehalfOfUnconsolidatedAffiliates" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_NetCashProvidedByUsedInDiscontinuedOperations" xlink:label="us-gaap_NetCashProvidedByUsedInDiscontinuedOperations" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" xlink:label="us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2012/elts/us-gaap-2012-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_ProfitLoss" order="3" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" order="4" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="uspi_LossOnEarlyRetirementOfDebt" order="5" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="uspi_ChangesInOperatingAndRelatedPartiesAssetsAndLiabilitiesAndNoncashItemsIncludedInNetIncomeLoss" order="6" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities" order="7" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" order="9" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="uspi_PurchasesAndSalesOfNewBusinessesAndEquityInterestsNet" order="10" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_PaymentsForProceedsFromOtherInvestingActivities" order="11" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivities" order="12" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_ProceedsFromIssuanceOfLongTermDebt" order="14" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_ProceedsFromPaymentsToMinorityShareholders" order="15" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_PaymentsOfDividendsMinorityInterest" order="16" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_PaymentsOfDividendsCommonStock" order="17" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="uspi_DecreaseIncreaseInCashHeldOnBehalfOfUnconsolidatedAffiliates" order="18" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities" order="19" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_NetCashProvidedByUsedInDiscontinuedOperations" order="20" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease" order="21" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CondensedFinancialStatementsCaptionsLineItems" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" order="22" />
  </link:definitionLink>
  <!-- Dimension Defaults -->
  <link:definitionLink xlink:type="extended" xlink:role="http://uspi.com/role/FinancialStatementsDetails3" xlink:title="06133 - Disclosure - Condensed Consolidating Financial Statements (Details 3)">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.sec.gov/dei/2012/dei-2012-01-31.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="dei_LegalEntityAxis" xlink:to="dei_EntityDomain" order="1" />
  </link:definitionLink>
</link:linkbase>
