<?xml version="1.0" encoding="us-ascii"?>
<!-- EDGAR Online I-Metrix Xcelerate Risk Return XBRL Schema Document, based on XBRL 2.1  http://www.edgar-online.com/ -->
<!-- Created (UTC): 9/26/2012 4:37:14 PM -->
<!-- XBRL File Set ID: a8064a0c-ba2c-44b1-8930-d9d57a2ff6b1 -->
<!-- App Version: 3.0.0.183, 5.1.2600.196608, 14.0 -->
<!-- Copyright (c) 2005-2012 EDGAR Online, Inc. All Rights Reserved. -->
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        <link:definition>010005 - Document - Risk/Return Summary {Unlabeled} (LargeCap Growth Fund (Prospectus Summary):)</link:definition>
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        <link:definition>010010 - Schedule - Shareholder Fees</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>010015 - Schedule - Annual Fund Operating Expenses</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>010020 - Schedule - Expense Example {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>010025 - Schedule - Expense Example, No Redemption {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>010030 - Schedule - Annual Total Returns</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>010035 - Schedule - Average Annual Total Returns {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>050005 - Document - Risk/Return Summary {Unlabeled} (LargeCap Value Fund (Prospectus Summary):)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>050010 - Schedule - Shareholder Fees</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>050015 - Schedule - Annual Fund Operating Expenses</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>050020 - Schedule - Expense Example {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>050025 - Schedule - Expense Example, No Redemption {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/BarChartData_P0001-S000007017Member" id="BarChartData_P0001-S000007017Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050030 - Schedule - Annual Total Returns</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/PerformanceTableData_P0001-S000007017Member" id="PerformanceTableData_P0001-S000007017Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050035 - Schedule - Average Annual Total Returns {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/RiskReturnDetailData_P0001-S000007017Member" id="RiskReturnDetailData_P0001-S000007017Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050040 - Disclosure - Risk/Return Detail Data {Elements} (LargeCap Value Fund (Prospectus Summary):)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>050045 - Document - Risk/Return Summary {Unlabeled} (MidCap Blend Fund (Prospectus Summary):)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/ShareholderFeesData_P0001-S000007075Member" id="ShareholderFeesData_P0001-S000007075Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050050 - Schedule - Shareholder Fees</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/OperatingExpensesData_P0001-S000007075Member" id="OperatingExpensesData_P0001-S000007075Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050055 - Schedule - Annual Fund Operating Expenses</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/ExpenseExample_P0001-S000007075Member" id="ExpenseExample_P0001-S000007075Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050060 - Schedule - Expense Example {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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        <link:definition>050065 - Schedule - Expense Example, No Redemption {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/BarChartData_P0001-S000007075Member" id="BarChartData_P0001-S000007075Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050070 - Schedule - Annual Total Returns</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/PerformanceTableData_P0001-S000007075Member" id="PerformanceTableData_P0001-S000007075Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050075 - Schedule - Average Annual Total Returns {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/RiskReturnDetailData_P0001-S000007075Member" id="RiskReturnDetailData_P0001-S000007075Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050080 - Disclosure - Risk/Return Detail Data {Elements} (MidCap Blend Fund (Prospectus Summary):)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/RiskReturn_P0001-S000007214Member" id="RiskReturn_P0001-S000007214Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050085 - Document - Risk/Return Summary {Unlabeled} (SmallCap Blend Fund (Prospectus Summary):)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/ShareholderFeesData_P0001-S000007214Member" id="ShareholderFeesData_P0001-S000007214Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050090 - Schedule - Shareholder Fees</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/OperatingExpensesData_P0001-S000007214Member" id="OperatingExpensesData_P0001-S000007214Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050095 - Schedule - Annual Fund Operating Expenses</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/ExpenseExample_P0001-S000007214Member" id="ExpenseExample_P0001-S000007214Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050100 - Schedule - Expense Example {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/ExpenseExampleNoRedemption_P0001-S000007214Member" id="ExpenseExampleNoRedemption_P0001-S000007214Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050105 - Schedule - Expense Example, No Redemption {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/BarChartData_P0001-S000007214Member" id="BarChartData_P0001-S000007214Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050110 - Schedule - Annual Total Returns</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/PerformanceTableData_P0001-S000007214Member" id="PerformanceTableData_P0001-S000007214Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050115 - Schedule - Average Annual Total Returns {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/RiskReturnDetailData_P0001-S000007214Member" id="RiskReturnDetailData_P0001-S000007214Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050120 - Disclosure - Risk/Return Detail Data {Elements} (SmallCap Blend Fund (Prospectus Summary):)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/RiskReturn_P0001-S000014240Member" id="RiskReturn_P0001-S000014240Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050125 - Document - Risk/Return Summary {Unlabeled} (Equity Income Fund formerly Equity Income Fund I (Prospectus Summary):)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/ShareholderFeesData_P0001-S000014240Member" id="ShareholderFeesData_P0001-S000014240Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050130 - Schedule - Shareholder Fees</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/OperatingExpensesData_P0001-S000014240Member" id="OperatingExpensesData_P0001-S000014240Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050135 - Schedule - Annual Fund Operating Expenses</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/ExpenseExample_P0001-S000014240Member" id="ExpenseExample_P0001-S000014240Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050140 - Schedule - Expense Example {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/ExpenseExampleNoRedemption_P0001-S000014240Member" id="ExpenseExampleNoRedemption_P0001-S000014240Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050145 - Schedule - Expense Example, No Redemption {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/BarChartData_P0001-S000014240Member" id="BarChartData_P0001-S000014240Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050150 - Schedule - Annual Total Returns</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/PerformanceTableData_P0001-S000014240Member" id="PerformanceTableData_P0001-S000014240Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050155 - Schedule - Average Annual Total Returns {Transposed}</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/RiskReturnDetailData_P0001-S000014240Member" id="RiskReturnDetailData_P0001-S000014240Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050160 - Disclosure - Risk/Return Detail Data {Elements} (Equity Income Fund formerly Equity Income Fund I (Prospectus Summary):)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
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      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/RiskReturn_P0001-S000024296Member" id="RiskReturn_P0001-S000024296Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050165 - Document - Risk/Return Summary {Unlabeled} (Global Diversified Income Fund (Prospectus Summary):)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.principalfunds.com/20120914/role/ShareholderFeesData_P0001-S000024296Member" id="ShareholderFeesData_P0001-S000024296Member" xmlns:link="http://www.xbrl.org/2003/linkbase">
        <link:definition>050170 - Schedule - Shareholder Fees</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
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        <link:definition>050175 - Schedule - Annual Fund Operating Expenses</link:definition>
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        <link:definition>050180 - Schedule - Expense Example {Transposed}</link:definition>
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        <link:definition>050185 - Schedule - Expense Example, No Redemption {Transposed}</link:definition>
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        <link:definition>050190 - Schedule - Annual Total Returns</link:definition>
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        <link:definition>050195 - Schedule - Average Annual Total Returns {Transposed}</link:definition>
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        <link:definition>050200 - Disclosure - Risk/Return Detail Data {Elements} (Global Diversified Income Fund (Prospectus Summary):)</link:definition>
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