497

	400 Howard Street P.O.Box 7101 San Francisco, CA 94105
	Tel +1 415 670 7987
	Fax +1 415 618 5462 edward.baer@blackrock.com

November 6, 2012

Securities and Exchange Commission

100 F Street, N.E.

Washington, DC 20549

RE: iShares Trust

Securities Act File No. 333-92935

Investment Company Act File No. 811-09729

Ladies and Gentlemen:

On behalf of the Registrant and pursuant to Rule 497(e) under the Securities Act of 1933, as amended, attached for filing are exhibits containing interactive data format risk/return summary information that mirrors the risk/return summary information in the 497 filed on October 23, 2012 to the prospectuses for the iShares Core Long-Term U.S. Bond ETF (the “Fund”). The purpose of the filing is to submit the 497 filed on October 23, 2012 in XBRL for the Fund.

If you have any questions regarding this filing, please contact Benjamin Haskin of Willkie Farr & Gallagher LLP at (202) 303-1124 or me at (415) 670-7987.

Very truly yours,

/s/ Edward Baer

Edward Baer

cc: Benjamin Haskin, Esq.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	iSHARES TRUST
Prospectus Date	rr_ProspectusDate	Jul. 01, 2012
Document Creation Date	dei_DocumentCreationDate	Oct. 23, 2012

XML

iShares Core Long-Term U.S. Bond ETF

iSHARES^® CORE LONG-TERM
U.S. BOND ETFTicker: ILTB Stock Exchange: NYSE Arca

Investment Objective

The iShares Core Long-Term U.S. Bond ETF (the “Fund”) seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Barclays U.S. Long Government/Credit Bond Index (the “Underlying Index”), which includes publicly-issued U.S. Treasury debt, U.S. government agency debt, taxable debt issued by U.S. states and territories and their political subdivisions, debt issued by U.S. and non-U.S. corporations, non-U.S. government debt and supranational debt.

Fees and Expenses

The following table describes the fees and expenses that you will incur if you own shares of the Fund. The investment advisory agreement between iShares Trust (the “Trust”) and BlackRock Fund Advisors (“BFA”) (the “Investment Advisory Agreement”) provides that BFA will pay all operating expenses of the Fund, except interest expenses, taxes, brokerage expenses, future distribution fees or expenses, and extraordinary expenses.

You may also incur usual and customary brokerage commissions when buying or selling shares of the Fund, which are not reflected in the example that follows:

Annual Fund Operating Expenses
(ongoing expenses that you pay each year as a
percentage of the value of your investments)

Annual Fund Operating Expenses	Management Fees	Distribution and Service (12b-1) Fees	Other Expenses	Total Annual Fund Operating Expenses
iShares Core Long-Term U.S. Bond ETF	0.12%	none	none	0.12%	[1]

Example.

This Example is intended to help you compare the cost of owning shares of the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

Expense Example (USD $)	1 Year	3 Years	5 Years	10 Years
iShares Core Long-Term U.S. Bond ETF	12	39	68	154

Portfolio Turnover.

The Fund may pay transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 12% of the average value of its portfolio.

Principal Investment Strategies

The Underlying Index is a sub-index of the Barclays U.S. Aggregate Bond Index and provides exposure to securities in the long maturity range of the Barclays U.S. Government/Credit Bond Index. The Barclays U.S. Government/Credit Bond Index is comprised of two combined indexes, the Barclays U.S. Government Bond Index and Barclays U.S. Credit Bond Index that are each a subcomponent of the Barclays U.S. Aggregate Bond Index. The Barclays U.S. Government Bond Index includes treasuries (i.e., public obligations of the U.S. Treasury that have remaining maturities of more than one year) and agencies (i.e., publicly issued debt of U.S. government agencies, quasi-federal corporations, and corporate or foreign debt guaranteed by the U.S. government). The Barclays U.S. Credit Bond Index includes publicly-issued U.S. dollar-denominated corporate, sovereign, supranational, and local authority debentures and secured notes that meet specified maturity, liquidity, and quality requirements. The securities in the Underlying Index have $250 million or more par amount outstanding and have at least ten years remaining to maturity or the first call date in the case of callable perpetual securities. In addition, the securities in the Underlying Index must be denominated in U.S. dollars and be non-convertible. The securities must be either a U.S. government security, a government-related security, or corporate security and must be rated investment-grade (Baa3/BBB-/BBB-) or higher using the middle rating of Moody’s^® Investors Service, Inc., Standard and Poor’s^® Ratings Service, or Fitch, Inc. after dropping the highest and lowest available ratings. When a rating from only two agencies is available, the lower (“more conservative”) rating is used. When a rating from only one agency is available, then that rating is used to determine index eligibility. The Underlying Index is rebalanced on the last calendar day of each month.

BFA uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued.

Indexing may eliminate the chance that the Fund will substantially outperform the Underlying Index but also may reduce some of the risks of active management, such as poor security selection. Indexing seeks to achieve lower costs and better after-tax performance by keeping portfolio turnover low in comparison to actively managed investment companies.

BFA uses a representative sampling indexing strategy to manage the Fund. “Representative sampling” is an indexing strategy that involves investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The securities selected are expected to have, in the aggregate, investment characteristics (based on factors such as market capitalization and industry weightings), fundamental characteristics (such as return variability, duration, maturity or credit ratings and yield) and liquidity measures similar to those of the Underlying Index. The Fund may or may not hold all of the securities in the Underlying Index.

The Fund generally invests at least 80% of its assets in the securities of the Underlying Index or in depositary receipts representing securities in the Underlying Index. The Fund may invest the remainder of its assets in certain futures, options and swap contracts, cash and cash equivalents, including money market funds advised by BFA or its affiliates, as well as in securities not included in the Underlying Index, but which BFA believes will help the Fund track the Underlying Index.

The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received).

The Underlying Index is sponsored by an organization (the “Index Provider”) that is independent of the Fund and BFA. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. The Fund’s Index Provider is Barclays Capital Inc. (“Barclays Capital”).

Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries, which may include large-, mid- or small-capitalization companies, to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities), repurchase agreements collateralized by U.S. government securities, and securities of state or municipal governments and their political subdivisions are not considered to be issued by members of any industry.

Summary of Principal Risks

As with any investment, you could lose all or part of your investment in the Fund, and the Fund’s performance could trail that of other investments. The Fund is subject to the principal risks noted below, any of which may adversely affect the Fund’s net asset value per share (“NAV”), trading price, yield, total return and ability to meet its investment objective.

Asset Class Risk. Securities in the Underlying Index or in the Fund’s portfolio may underperform in comparison to the general securities markets or other asset classes.

Call Risk. During periods of falling interest rates, an issuer of a callable bond held by the Fund may “call” or repay the security before its stated maturity, and the Fund may have to reinvest the proceeds at lower interest rates, resulting in a decline in the Fund’s income.

Concentration Risk. To the extent that the Fund’s investments are concentrated in a particular sovereign entity or entities, in a particular country, group of countries, market, sector or asset class, the Fund may be susceptible to loss due to adverse occurrences affecting that sovereign entity or entities, in a particular country, group of countries, market, sector or asset class.

Credit Risk. The Fund is subject to the risk that debt issuers and other counterparties may not honor their obligations or may have their debt downgraded by ratings agencies.

Custody Risk. Less developed markets are more likely to experience problems with the clearing and settling of trades and the holding of securities by local banks, agents and depositories.

Extension Risk. During periods of rising interest rates, certain obligations will be paid off substantially more slowly than originally anticipated and the value of those securities may fall sharply, resulting in a decline to the Fund’s income and potentially in the value of the Fund’s investments.

Financial Sector Risk. Performance of companies in the financial sector may be adversely impacted by many factors, including, among others, government regulations, economic conditions, credit rating downgrades, changes in interest rates, and decreased liquidity in credit markets. This sector has experienced significant losses in the recent past, and the impact of more stringent capital requirements and of recent or future regulation on any individual financial company or on the sector as a whole cannot be predicted.

Geographic Risk. A natural or other disaster could occur in a geographic region in which the Fund invests.

Income Risk. The Fund’s income may decline when interest rates fall. This decline can occur because the Fund must invest in lower-yielding bonds as bonds in its portfolio mature, bonds in the Underlying Index are substituted or the Fund otherwise needs to purchase additional bonds.

Industrials Sector Risk. The industrials sector may be affected by changes in the supply and demand for products and services, product obsolescence, claims for environmental damage or product liability and general economic conditions, among other factors.

Interest Rate Risk. An increase in interest rates may cause the value of fixed-income securities held by the Fund to decline.

Issuer Risk. Fund performance depends on the performance of individual securities to which the Fund has exposure. Changes to the financial condition or credit rating of an issuer of those securities may cause the value of the securities to decline.

Liquidity Risk. Liquidity risk exists when particular investments are difficult to purchase or sell. This can reduce the Fund’s returns because the Fund may be unable to transact at advantageous times or prices.

Management Risk. As the Fund may not fully replicate the Underlying Index, it is subject to the risk that BFA’s investment management strategy may not produce the intended results.

Market Risk. The Fund could lose money over short periods due to short-term market movements and over longer periods during market downturns.

Market Trading Risk. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS, AMONG OTHERS, MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Non-Diversification Risk. The Fund may invest a large percentage of its assets in securities issued by or representing a small number of issuers. As a result, the Fund’s performance may depend on the performance of a small number of issuers.

Non-U.S. Issuers Risk. Securities issued by non-U.S. issuers carry different risks from securities issued by U.S. issuers. These include differences in accounting, auditing and financial reporting standards, the possibility of expropriation or confiscatory taxation, adverse changes in investment or exchange control regulations, political instability, regulatory and economic differences, and potential restrictions on the flow of international capital. The Fund is specifically exposed to North American Economic Risk.

North American Economic Risk. The United States is Canada’s and Mexico’s largest trading and investment partner. Economic events in any one North American country can have a significant economic effect on the entire North American region, and on some or all of the North American countries in which the Fund invests.

Passive Investment Risk. The Fund is not actively managed and BFA does not attempt to take defensive positions under any market conditions, including declining markets.

Reliance on Trading Partners Risk. The Fund invests in countries whose economies are heavily dependent upon trading with key partners. Any reduction in this trading may have an adverse impact on the Fund’s investments. Through its trading partners, the Fund is specifically exposed to U.S. Economic Risk.

Securities Lending Risk. The Fund may engage in securities lending. Securities lending involves the risk that the Fund may lose money because the borrower of the Fund’s loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of the collateral provided for loaned securities or a decline in the value of any investments made with cash collateral. These events could also trigger adverse tax consequences for the Fund.

Security Risk. Some countries and regions in which the Fund invests have experienced security concerns. Incidents involving a country’s or region’s security may cause uncertainty in these markets and may adversely affect their economies and the Fund’s investments.

Sovereign Obligations Risk. The Fund invests in securities issued by or guaranteed by sovereign governments, which may be unable or unwilling to repay principal or interest when due. In times of economic uncertainty, the prices of these securities may be more volatile than those of corporate debt obligations or of other government debt obligations.

Structural Risk. The countries in which the Fund invests may be subject to considerable degrees of economic, political and social instability.

Tracking Error Risk. Tracking error is the divergence of the Fund’s performance from that of the Underlying Index. Tracking error may occur because of imperfect correlation between the Fund’s holdings of portfolio securities and those in the Underlying Index, pricing differences, the Fund’s holding of cash, differences on timing of the accrual of dividends, changes to the Underlying Index or the need to meet various regulatory requirements. This risk may be heightened during times of increased market volatility or other unusual market conditions. Tracking error also may result because the Fund incurs fees and expenses, while the Underlying Index does not. BFA expects that the Fund may experience higher tracking error than is typical for similar index ETFs.

U.S. Government Issuers Risk. Treasury obligations may differ in their interest rates, maturities, times of issuance and other characteristics. Obligations of U.S. government agencies and authorities are supported by varying degrees of credit, but generally are not backed by the full faith and credit of the U.S. government. Similar to other issuers, changes to the financial condition or credit rating of the U.S. government or U.S. government agencies and authorities may cause the value of the Fund’s investments to decline.

Valuation Risk. The sales price the Fund could receive for a security may differ from the Fund’s valuation of the security and may differ from the value used by the Underlying Index, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.

Performance Information

The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund. Both assume that all dividends and distributions have been reinvested in the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Supplemental information about the Fund’s performance is shown under the heading Total Return Information in the Supplemental Information section of the Fund’s prospectus (the “Prospectus”).

Year by Year Returns (Year Ended December 31)

The best calendar quarter return during the period shown above was 15.37% in the 3rd quarter of 2011; the worst was -5.46% in the 4th quarter of 2010.
Updated performance information is available at www.iShares.com or by calling 1-800-iShares (1-800-474-2737) (toll free).

Average Annual Total Returns
(for the periods ended December 31, 2011)

Average Annual Total Returns		One Year	Since Fund Inception	Inception Date
iShares Core Long-Term U.S. Bond ETF		21.68%	14.05%	Dec. 08, 2009
iShares Core Long-Term U.S. Bond ETF Return After Taxes on Distributions	[1]	19.79%	12.26%
iShares Core Long-Term U.S. Bond ETF Return After Taxes on Distributions and Sale of Fund Shares	[1]	13.96%	10.92%
iShares Core Long-Term U.S. Bond ETF Barclays U.S. Long Government/Credit Bond Index (Index returns do not reflect deductions for fees, expenses, or taxes)	[2]	22.49%	14.62%
iShares Core Long-Term U.S. Bond ETF BofA Merrill Lynch 10+ Year US Corporate & Government Index (Index returns do not reflect deductions for fees, expenses, or taxes)		21.98%	14.57%

[1] The expense information in the table above has been restated to reflect current fees.

[1] The Fund's total return for the three months ended March 31, 2012 was -1.89%.

[1] After-tax returns in the table above are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state or local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown, and after-tax returns shown are not relevant to tax-exempt investors or investors who hold shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts ("IRAs"). Fund returns after taxes on distributions and sale of Fund shares are calculated assuming that an investor has sufficient capital gains of the same character from other investments to offset any capital losses from the sale of Fund shares. As a result, Fund returns after taxes on distributions and sale of Fund shares may exceed Fund returns before taxes and/or returns after taxes on distributions.

[2] On October 23, 2012, the Fund's Underlying Index changed from BofA Merrill Lynch 10+ Year US Corporate & Government IndexSM to Barclays U.S. Long Government/Credit Bond Index. The performance of both the former Underlying Index and the current Underlying Index are shown.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

iSHARES TRUST

Prospectus Date

rr_ProspectusDate

Jul. 01, 2012

iShares Core Long-Term U.S. Bond ETF

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

iSHARES^® CORE LONG-TERM
U.S. BOND ETFTicker: ILTB Stock Exchange: NYSE Arca

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The iShares Core Long-Term U.S. Bond ETF (the “Fund”) seeks investment results that correspond generally to the price and yield performance, before fees and expenses, of the Barclays U.S. Long Government/Credit Bond Index (the “Underlying Index”), which includes publicly-issued U.S. Treasury debt, U.S. government agency debt, taxable debt issued by U.S. states and territories and their political subdivisions, debt issued by U.S. and non-U.S. corporations, non-U.S. government debt and supranational debt.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that you will incur if you own shares of the Fund. The investment advisory agreement between iShares Trust (the “Trust”) and BlackRock Fund Advisors (“BFA”) (the “Investment Advisory Agreement”) provides that BFA will pay all operating expenses of the Fund, except interest expenses, taxes, brokerage expenses, future distribution fees or expenses, and extraordinary expenses.

You may also incur usual and customary brokerage commissions when buying or selling shares of the Fund, which are not reflected in the example that follows:

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(ongoing expenses that you pay each year as a
percentage of the value of your investments)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover.

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund may pay transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 12% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

12.00%

Expense Exchange Traded Fund Commissions [Text]

rr_ExpenseExchangeTradedFundCommissions

You may also incur usual and customary brokerage commissions when buying or selling shares of the Fund, which are not reflected in the example that follows:

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The expense information in the table above has been restated to reflect current fees.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example.

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of owning shares of the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Underlying Index is a sub-index of the Barclays U.S. Aggregate Bond Index and provides exposure to securities in the long maturity range of the Barclays U.S. Government/Credit Bond Index. The Barclays U.S. Government/Credit Bond Index is comprised of two combined indexes, the Barclays U.S. Government Bond Index and Barclays U.S. Credit Bond Index that are each a subcomponent of the Barclays U.S. Aggregate Bond Index. The Barclays U.S. Government Bond Index includes treasuries (i.e., public obligations of the U.S. Treasury that have remaining maturities of more than one year) and agencies (i.e., publicly issued debt of U.S. government agencies, quasi-federal corporations, and corporate or foreign debt guaranteed by the U.S. government). The Barclays U.S. Credit Bond Index includes publicly-issued U.S. dollar-denominated corporate, sovereign, supranational, and local authority debentures and secured notes that meet specified maturity, liquidity, and quality requirements. The securities in the Underlying Index have $250 million or more par amount outstanding and have at least ten years remaining to maturity or the first call date in the case of callable perpetual securities. In addition, the securities in the Underlying Index must be denominated in U.S. dollars and be non-convertible. The securities must be either a U.S. government security, a government-related security, or corporate security and must be rated investment-grade (Baa3/BBB-/BBB-) or higher using the middle rating of Moody’s^® Investors Service, Inc., Standard and Poor’s^® Ratings Service, or Fitch, Inc. after dropping the highest and lowest available ratings. When a rating from only two agencies is available, the lower (“more conservative”) rating is used. When a rating from only one agency is available, then that rating is used to determine index eligibility. The Underlying Index is rebalanced on the last calendar day of each month.

BFA uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued.

Indexing may eliminate the chance that the Fund will substantially outperform the Underlying Index but also may reduce some of the risks of active management, such as poor security selection. Indexing seeks to achieve lower costs and better after-tax performance by keeping portfolio turnover low in comparison to actively managed investment companies.

BFA uses a representative sampling indexing strategy to manage the Fund. “Representative sampling” is an indexing strategy that involves investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The securities selected are expected to have, in the aggregate, investment characteristics (based on factors such as market capitalization and industry weightings), fundamental characteristics (such as return variability, duration, maturity or credit ratings and yield) and liquidity measures similar to those of the Underlying Index. The Fund may or may not hold all of the securities in the Underlying Index.

The Fund generally invests at least 80% of its assets in the securities of the Underlying Index or in depositary receipts representing securities in the Underlying Index. The Fund may invest the remainder of its assets in certain futures, options and swap contracts, cash and cash equivalents, including money market funds advised by BFA or its affiliates, as well as in securities not included in the Underlying Index, but which BFA believes will help the Fund track the Underlying Index.

The Fund may lend securities representing up to one-third of the value of the Fund’s total assets (including the value of the collateral received).

The Underlying Index is sponsored by an organization (the “Index Provider”) that is independent of the Fund and BFA. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. The Fund’s Index Provider is Barclays Capital Inc. (“Barclays Capital”).

Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries, which may include large-, mid- or small-capitalization companies, to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities), repurchase agreements collateralized by U.S. government securities, and securities of state or municipal governments and their political subdivisions are not considered to be issued by members of any industry.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries, which may include large-, mid- or small-capitalization companies, to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities), repurchase agreements collateralized by U.S. government securities, and securities of state or municipal governments and their political subdivisions are not considered to be issued by members of any industry.

Risk [Heading]

rr_RiskHeading

Summary of Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any investment, you could lose all or part of your investment in the Fund, and the Fund’s performance could trail that of other investments. The Fund is subject to the principal risks noted below, any of which may adversely affect the Fund’s net asset value per share (“NAV”), trading price, yield, total return and ability to meet its investment objective.

Asset Class Risk. Securities in the Underlying Index or in the Fund’s portfolio may underperform in comparison to the general securities markets or other asset classes.

Call Risk. During periods of falling interest rates, an issuer of a callable bond held by the Fund may “call” or repay the security before its stated maturity, and the Fund may have to reinvest the proceeds at lower interest rates, resulting in a decline in the Fund’s income.

Concentration Risk. To the extent that the Fund’s investments are concentrated in a particular sovereign entity or entities, in a particular country, group of countries, market, sector or asset class, the Fund may be susceptible to loss due to adverse occurrences affecting that sovereign entity or entities, in a particular country, group of countries, market, sector or asset class.

Credit Risk. The Fund is subject to the risk that debt issuers and other counterparties may not honor their obligations or may have their debt downgraded by ratings agencies.

Custody Risk. Less developed markets are more likely to experience problems with the clearing and settling of trades and the holding of securities by local banks, agents and depositories.

Extension Risk. During periods of rising interest rates, certain obligations will be paid off substantially more slowly than originally anticipated and the value of those securities may fall sharply, resulting in a decline to the Fund’s income and potentially in the value of the Fund’s investments.

Financial Sector Risk. Performance of companies in the financial sector may be adversely impacted by many factors, including, among others, government regulations, economic conditions, credit rating downgrades, changes in interest rates, and decreased liquidity in credit markets. This sector has experienced significant losses in the recent past, and the impact of more stringent capital requirements and of recent or future regulation on any individual financial company or on the sector as a whole cannot be predicted.

Geographic Risk. A natural or other disaster could occur in a geographic region in which the Fund invests.

Income Risk. The Fund’s income may decline when interest rates fall. This decline can occur because the Fund must invest in lower-yielding bonds as bonds in its portfolio mature, bonds in the Underlying Index are substituted or the Fund otherwise needs to purchase additional bonds.

Industrials Sector Risk. The industrials sector may be affected by changes in the supply and demand for products and services, product obsolescence, claims for environmental damage or product liability and general economic conditions, among other factors.

Interest Rate Risk. An increase in interest rates may cause the value of fixed-income securities held by the Fund to decline.

Issuer Risk. Fund performance depends on the performance of individual securities to which the Fund has exposure. Changes to the financial condition or credit rating of an issuer of those securities may cause the value of the securities to decline.

Liquidity Risk. Liquidity risk exists when particular investments are difficult to purchase or sell. This can reduce the Fund’s returns because the Fund may be unable to transact at advantageous times or prices.

Management Risk. As the Fund may not fully replicate the Underlying Index, it is subject to the risk that BFA’s investment management strategy may not produce the intended results.

Market Risk. The Fund could lose money over short periods due to short-term market movements and over longer periods during market downturns.

Market Trading Risk. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruption in the creation/redemption process of the Fund. ANY OF THESE FACTORS, AMONG OTHERS, MAY LEAD TO THE FUND’S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Non-Diversification Risk. The Fund may invest a large percentage of its assets in securities issued by or representing a small number of issuers. As a result, the Fund’s performance may depend on the performance of a small number of issuers.

Non-U.S. Issuers Risk. Securities issued by non-U.S. issuers carry different risks from securities issued by U.S. issuers. These include differences in accounting, auditing and financial reporting standards, the possibility of expropriation or confiscatory taxation, adverse changes in investment or exchange control regulations, political instability, regulatory and economic differences, and potential restrictions on the flow of international capital. The Fund is specifically exposed to North American Economic Risk.

North American Economic Risk. The United States is Canada’s and Mexico’s largest trading and investment partner. Economic events in any one North American country can have a significant economic effect on the entire North American region, and on some or all of the North American countries in which the Fund invests.

Passive Investment Risk. The Fund is not actively managed and BFA does not attempt to take defensive positions under any market conditions, including declining markets.

Reliance on Trading Partners Risk. The Fund invests in countries whose economies are heavily dependent upon trading with key partners. Any reduction in this trading may have an adverse impact on the Fund’s investments. Through its trading partners, the Fund is specifically exposed to U.S. Economic Risk.

Securities Lending Risk. The Fund may engage in securities lending. Securities lending involves the risk that the Fund may lose money because the borrower of the Fund’s loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of the collateral provided for loaned securities or a decline in the value of any investments made with cash collateral. These events could also trigger adverse tax consequences for the Fund.

Security Risk. Some countries and regions in which the Fund invests have experienced security concerns. Incidents involving a country’s or region’s security may cause uncertainty in these markets and may adversely affect their economies and the Fund’s investments.

Sovereign Obligations Risk. The Fund invests in securities issued by or guaranteed by sovereign governments, which may be unable or unwilling to repay principal or interest when due. In times of economic uncertainty, the prices of these securities may be more volatile than those of corporate debt obligations or of other government debt obligations.

Structural Risk. The countries in which the Fund invests may be subject to considerable degrees of economic, political and social instability.

Tracking Error Risk. Tracking error is the divergence of the Fund’s performance from that of the Underlying Index. Tracking error may occur because of imperfect correlation between the Fund’s holdings of portfolio securities and those in the Underlying Index, pricing differences, the Fund’s holding of cash, differences on timing of the accrual of dividends, changes to the Underlying Index or the need to meet various regulatory requirements. This risk may be heightened during times of increased market volatility or other unusual market conditions. Tracking error also may result because the Fund incurs fees and expenses, while the Underlying Index does not. BFA expects that the Fund may experience higher tracking error than is typical for similar index ETFs.

U.S. Government Issuers Risk. Treasury obligations may differ in their interest rates, maturities, times of issuance and other characteristics. Obligations of U.S. government agencies and authorities are supported by varying degrees of credit, but generally are not backed by the full faith and credit of the U.S. government. Similar to other issuers, changes to the financial condition or credit rating of the U.S. government or U.S. government agencies and authorities may cause the value of the Fund’s investments to decline.

Valuation Risk. The sales price the Fund could receive for a security may differ from the Fund’s valuation of the security and may differ from the value used by the Underlying Index, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.

Risk Lose Money [Text]

rr_RiskLoseMoney

As with any investment, you could lose all or part of your investment in the Fund, and the Fund’s performance could trail that of other investments.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Non-Diversification Risk. The Fund may invest a large percentage of its assets in securities issued by or representing a small number of issuers. As a result, the Fund’s performance may depend on the performance of a small number of issuers.

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund. Both assume that all dividends and distributions have been reinvested in the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Supplemental information about the Fund’s performance is shown under the heading Total Return Information in the Supplemental Information section of the Fund’s prospectus (the “Prospectus”).

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-iShares (1-800-474-2737) (toll free)

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.iShares.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.

Bar Chart [Heading]

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Year by Year Returns (Year Ended December 31)

Bar Chart Closing [Text Block]

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The best calendar quarter return during the period shown above was 15.37% in the 3rd quarter of 2011; the worst was -5.46% in the 4th quarter of 2010.
Updated performance information is available at www.iShares.com or by calling 1-800-iShares (1-800-474-2737) (toll free).

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
(for the periods ended December 31, 2011)

Performance Table Market Index Changed

rr_PerformanceTableMarketIndexChanged

On October 23, 2012, the Fund’s Underlying Index changed from BofA Merrill Lynch 10+ Year US Corporate & Government Index^SM to Barclays U.S. Long Government/Credit Bond Index. The performance of both the former Underlying Index and the current Underlying Index are shown.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns in the table above are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state or local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on an investor’s tax situation and may differ from those shown, and after-tax returns shown are not relevant to tax-exempt investors or investors who hold shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”).

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

Fund returns after taxes on distributions and sale of Fund shares are calculated assuming that an investor has sufficient capital gains of the same character from other investments to offset any capital losses from the sale of Fund shares. As a result, Fund returns after taxes on distributions and sale of Fund shares may exceed Fund returns before taxes and/or returns after taxes on distributions.

iShares Core Long-Term U.S. Bond ETF | iShares Core Long-Term U.S. Bond ETF

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.12%

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

none

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.12%

^[1]

1 Year

rr_ExpenseExampleYear01

12

3 Years

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39

5 Years

rr_ExpenseExampleYear05

68

10 Years

rr_ExpenseExampleYear10

154

2010

rr_AnnualReturn2010

9.89%

^[2]

2011

rr_AnnualReturn2011

21.68%

^[2]

Year to Date Return, Label

rr_YearToDateReturnLabel

The Fund’s total return for the three months ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(1.89%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

best

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2011

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

15.37%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

worst

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(5.46%)

One Year

rr_AverageAnnualReturnYear01

21.68%

Since Fund Inception

rr_AverageAnnualReturnSinceInception

14.05%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 08, 2009

iShares Core Long-Term U.S. Bond ETF | Return After Taxes on Distributions | iShares Core Long-Term U.S. Bond ETF

Risk/Return:

rr_RiskReturnAbstract

One Year

rr_AverageAnnualReturnYear01

19.79%

^[3]

Since Fund Inception

rr_AverageAnnualReturnSinceInception

12.26%

^[3]

iShares Core Long-Term U.S. Bond ETF | Return After Taxes on Distributions and Sale of Fund Shares | iShares Core Long-Term U.S. Bond ETF

Risk/Return:

rr_RiskReturnAbstract

One Year

rr_AverageAnnualReturnYear01

13.96%

^[3]

Since Fund Inception

rr_AverageAnnualReturnSinceInception

10.92%

^[3]

iShares Core Long-Term U.S. Bond ETF | Barclays U.S. Long Government/Credit Bond Index (Index returns do not reflect deductions for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

One Year

rr_AverageAnnualReturnYear01

22.49%

^[4]

Since Fund Inception

rr_AverageAnnualReturnSinceInception

14.62%

^[4]

iShares Core Long-Term U.S. Bond ETF | BofA Merrill Lynch 10+ Year US Corporate & Government Index (Index returns do not reflect deductions for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

One Year

rr_AverageAnnualReturnYear01

21.98%

Since Fund Inception

rr_AverageAnnualReturnSinceInception

14.57%

[1] The expense information in the table above has been restated to reflect current fees.

[2] The Fund's total return for the three months ended March 31, 2012 was -1.89%.

[3] After-tax returns in the table above are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state or local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown, and after-tax returns shown are not relevant to tax-exempt investors or investors who hold shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts ("IRAs"). Fund returns after taxes on distributions and sale of Fund shares are calculated assuming that an investor has sufficient capital gains of the same character from other investments to offset any capital losses from the sale of Fund shares. As a result, Fund returns after taxes on distributions and sale of Fund shares may exceed Fund returns before taxes and/or returns after taxes on distributions.

[4] On October 23, 2012, the Fund's Underlying Index changed from BofA Merrill Lynch 10+ Year US Corporate & Government IndexSM to Barclays U.S. Long Government/Credit Bond Index. The performance of both the former Underlying Index and the current Underlying Index are shown.