Vanguard Total Bond Market Index Fund

Summary Prospectus 

April 26, 2011

Investor Shares for Participants

Vanguard Total Bond Market Index Fund Investor Shares (VBMFX)

The Fund’s statutory Prospectus and Statement of Additional Information dated

April 26, 2011, are incorporated into and made part of this Summary Prospectus

by reference.

Before you invest, you may want to review the Fund’s Prospectus, which

contains more information about the Fund and its risks. You can find

the Fund’s Prospectus and other information about the Fund online at

www.vanguard.com/prospectus. You can also get this information at no

cost by calling 800-523-1188 or by sending an e-mail request to

online@vanguard.com.

The Securities and Exchange Commission (SEC) has not approved or disapproved these securities or

passed upon the adequacy of this prospectus. Any representation to the contrary is a criminal offense.

Investment Objective
The Fund seeks to track the performance of a broad, market-weighted bond index.

Fees and Expenses
The following table describes the fees and expenses you may pay if you buy and hold
Investor Shares of the Fund.

Shareholder Fees
(Fees paid directly from your investment)
Sales Charge (Load) Imposed on Purchases	None
Purchase Fee	None
Sales Charge (Load) Imposed on Reinvested Dividends	None
Redemption Fee	None

Annual Fund Operating Expenses
(Expenses that you pay each year as a percentage of the value of your investment)
Management Expenses	0.19%
12b-1 Distribution Fee	None
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.22%

Example

The following example is intended to help you compare the cost of investing in the
Fund’s Investor Shares with the cost of investing in other mutual funds. It illustrates
the hypothetical expenses that you would incur over various periods if you invest
$10,000 in the Fund’s shares. This example assumes that the Shares provide a return
of 5% a year and that operating expenses remain as stated in the preceding table. The
results apply whether or not you redeem your investment at the end of the given
period. Although your actual costs may be higher or lower, based on these
assumptions your costs would be:

1 Year	3 Years	5 Years	10 Years
$23	$71	$124	$280

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Portfolio Turnover

The Fund pays 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 previous expense example, reduce the Fund’s performance. During
the most recent fiscal year, the Fund’s portfolio turnover rate was 75%.

Primary Investment Strategies
The Fund employs a “passive management”—or indexing—investment approach
designed to track the performance of the Barclays Capital U.S. Aggregate Float
Adjusted Index. This Index represents a wide spectrum of public, investment-grade,
taxable, fixed income securities in the United States—including government,
corporate, and international dollar-denominated bonds, as well as mortgage-backed
and asset-backed securities—all with maturities of more than 1 year.

The Fund invests by sampling the Index, meaning that it holds a broadly diversified
collection of securities that, in the aggregate, approximates the full Index in terms of key
risk factors and other characteristics. All of the Fund’s investments will be selected
through the sampling process, and at least 80% of the Fund’s assets will be invested in
bonds held in the Index. The Fund maintains a dollar-weighted average maturity
consistent with that of the Index, which generally ranges between 5 and 10 years.

Primary Risks
An investment in the Fund could lose money over short or even long periods. You should
expect the Fund’s share price and total return to fluctuate within a wide range, like the
fluctuations of the overall bond market. The Fund’s performance could be hurt by:

• Interest rate risk, which is the chance that bond prices overall will decline because
of rising interest rates. Interest rate risk should be moderate for the Fund because it
invests mainly in short- and intermediate-term bonds, whose prices are less sensitive
to interest rate changes than are the prices of long-term bonds.

• Income risk, which is the chance that the Fund’s income will decline because of
falling interest rates. Income risk is generally moderate for intermediate-term bond
funds, so investors should expect the Fund’s monthly income to fluctuate accordingly.

• Credit risk, which is the chance that a bond issuer will fail to pay interest and
principal in a timely manner, or that negative perceptions of the issuer’s ability to
make such payments will cause the price of that bond to decline. Credit risk should be
low for the Fund because it purchases only bonds that are of investment-grade quality.

• Call risk, which is the chance that during periods of falling interest rates, issuers of
callable bonds may call (redeem) securities with higher coupons or interest rates

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before their maturity dates. The Fund would then lose any price appreciation above
the bond’s call price and would be forced to reinvest the unanticipated proceeds at
lower interest rates, resulting in a decline in the Fund’s income. For mortgage-backed
securities, this risk is known as prepayment risk. Call/prepayment risk should be
moderate for the Fund because it invests only a portion of its assets in callable bonds
and mortgage-backed securities.

• Index sampling risk, which is the chance that the securities selected for the Fund, in
the aggregate, will not provide investment performance matching that of the Fund’s
target index. Index sampling risk for the Fund should be low.

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed
by the Federal Deposit Insurance Corporation or any other government agency.

Annual Total Returns
The following bar chart and table are intended to help you understand the risks of
investing in the Fund. The bar chart shows how the performance of the Fund‘s
Investor Shares has varied from one calendar year to another over the periods shown.
The table shows how the average annual total returns compare with those of the
Fund‘s target index and other comparative indexes, which have investment
characteristics similar to those of the Fund. Keep in mind that the Fund’s past
performance does not indicate how the Fund will perform in the future. Updated
performance information is available on our website at vanguard.com/performance or
by calling Vanguard toll-free at 800-662-7447.

Annual Total Returns — Vanguard Total Bond Market Index Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter
was 4.37% (quarter ended December 31, 2008), and the lowest return for a quarter
was –2.49% (quarter ended June 30, 2004).

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Average Annual Total Returns for Periods Ended December 31, 2010
	1 Year	5 Years	10 Years
Vanguard Total Bond Market Index Fund Investor Shares	6.42%	5.72%	5.57%
Comparative Indexes
(reflect no deduction for fees or expenses)
Spliced Barclays Capital U.S. Aggregate Float Adjusted Index	6.58%	5.81%	5.84%
Barclays Capital U.S. Aggregate Float Adjusted Index	6.58	—	—
Barclays Capital U.S. Aggregate Bond Index	6.54	5.80	5.84

Investment Advisor
The Vanguard Group, Inc.

Portfolio Managers

Gregory Davis, CFA, Principal of Vanguard and head of Vanguard’s Bond Index Group.
He has co-managed the Fund since 2008.

Kenneth E. Volpert, CFA, Principal of Vanguard and head of Vanguard’s Taxable Bond
Group. He has managed the Fund since 1992 (co-managed since 2008).

Tax Information
The Fund’s distributions will be reinvested in additional Fund shares and accumulate on
a tax-deferred basis if you are investing through an employer-sponsored retirement or
savings plan. You will not owe taxes on these distributions until you begin withdrawals
from the plan. You should consult your plan administrator, your plan’s Summary Plan
Description, or your tax advisor about the tax consequences of plan withdrawals.

Payments to Financial Intermediaries
The Fund and its investment advisor do not pay financial intermediaries for sales of
Fund shares.

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Vanguard Total Bond Market Index Fund Investor Shares—Fund Number 84
CFA® is a trademark owned by CFA Institute.
© 2011 The Vanguard Group, Inc. All rights reserved.
Vanguard Marketing Corporation, Distributor.
	SPI 084 042011