Vanguard Mid-Cap Index Fund 

Summary Prospectus 

September 27, 2011 

Investor Shares for Participants 

Vanguard Mid-Cap Index Fund Investor Shares (VIMSX) 

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

September 27, 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 benchmark index that measures the
investment return of mid-capitalization stocks.

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	0.23%
12b-1 Distribution Fee	None
Other Expenses	0.03%
Total Annual Fund Operating Expenses	0.26%

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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
$27	$84	$146	$331

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 16%.

Primary Investment Strategies
The Fund employs a “passive management”—or indexing—investment approach
designed to track the performance of the MSCI US Mid Cap 450 Index, a broadly
diversified index of stocks of medium-size U.S. companies. The Fund attempts to
replicate the target index by investing all, or substantially all, of its assets in the stocks
that make up the Index, holding each stock in approximately the same proportion as
its weighting in the Index.

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 stock market. The Fund’s performance could be hurt by:

• Stock market risk, which is the chance that stock prices overall will decline. Stock
markets tend to move in cycles, with periods of rising prices and periods of falling prices.
The Fund’s target index may, at times, become focused in stocks of a particular sector,
category, or group of companies. Because the Fund seeks to track its target index, the
Fund may underperform the overall stock market.

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• Investment style risk, which is the chance that returns from mid-capitalization
stocks will trail returns from the overall stock market. Historically, mid-cap stocks have
been more volatile in price than the large-cap stocks that dominate the overall market,
and they often perform quite differently. Mid-cap stocks tend to have greater volatility
than large-cap stocks because, among other things, medium-size companies are more
sensitive to changing economic conditions.

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 Mid-Cap Index Fund Investor Shares

During the periods shown in the bar chart, the highest return for a calendar quarter
was 21.53% (quarter ended September 30, 2009), and the lowest return for a quarter
was –25.63% (quarter ended December 31, 2008).

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Average Annual Total Returns for Periods Ended December 31, 2010
	1 Year	5 Years	10 Years
Vanguard Mid-Cap Index Fund Investor Shares	25.46%	4.27%	6.78%
Comparative Indexes
(reflect no deduction for fees or expenses)
S&P MidCap 400 Index	26.64%	5.74%	7.16%
Spliced Mid Cap Index	25.69	4.42	6.84
MSCI US Mid Cap 450 Index	25.69	4.42	—

Investment Advisor
The Vanguard Group, Inc.

Portfolio Manager

Donald M. Butler, CFA, Principal of Vanguard. He has managed the Fund since its
inception in 1998.

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 Mid-Cap Index Fund Investor Shares—Fund Number 859

CFA^® is a trademark owned by CFA Institute.

THIS FUND IS NOT SPONSORED, ENDORSED, SOLD OR PROMOTED BY MSCI INC. (“MSCI”), ANY OF ITS AFFILIATES, ANY OF ITS
DIRECT OR INDIRECT INFORMATION PROVIDERS OR ANY OTHER THIRD PARTY INVOLVED IN, OR RELATED TO, COMPILING,
COMPUTING OR CREATING ANY MSCI INDEX (COLLECTIVELY, THE “MSCI PARTIES”). THE MSCI INDEXES ARE THE EXCLUSIVE
PROPERTY OF MSCI. MSCI AND THE MSCI INDEX NAMES ARE SERVICE MARK(S) OF MSCI OR ITS AFFILIATES AND HAVE BEEN
LICENSED FOR USE FOR CERTAIN PURPOSES BY VANGUARD. NONE OF THE MSCI PARTIES MAKES ANY REPRESENTATION OR
WARRANTY, EXPRESS OR IMPLIED, TO THE OWNERS OF THIS FUND OR ANY MEMBER OF THE PUBLIC REGARDING THE
ADVISABILITY OF INVESTING IN FUNDS GENERALLY OR IN THIS FUND PARTICULARLY OR THE ABILITY OF ANY MSCI INDEX TO
TRACK CORRESPONDING STOCK MARKET PERFORMANCE. MSCI OR ITS AFFILIATES ARE THE LICENSORS OF CERTAIN
TRADEMARKS, SERVICE MARKS AND TRADE NAMES AND OF THE MSCI INDEXES WHICH ARE DETERMINED, COMPOSED
AND CALCULATED BY MSCI WITHOUT REGARD TO THIS FUND OR THE ISSUER OR OWNER OF THIS FUND. NONE OF THE MSCI
PARTIES HAS ANY OBLIGATION TO TAKE THE NEEDS OF THE ISSUERS OR OWNERS OF THIS FUND INTO CONSIDERATION IN
DETERMINING, COMPOSING OR CALCULATING THE MSCI INDEXES. NONE OF THE MSCI PARTIES IS RESPONSIBLE FOR OR
HAS PARTICIPATED IN THE DETERMINATION OF THE TIMING OF, PRICES AT, OR QUANTITIES OF THIS FUND TO BE ISSUED OR IN
THE DETERMINATION OR CALCULATION OF THE CONSIDERATION INTO WHICH THIS FUND IS REDEEMABLE. NONE OF THE
MSCI PARTIES HAS ANY OBLIGATION OR LIABILITY TO THE OWNERS OF THIS FUND IN CONNECTION WITH THE
ADMINISTRATION, MARKETING OR OFFERING OF THIS FUND.

ALTHOUGH MSCI SHALL OBTAIN INFORMATION FOR INCLUSION IN OR FOR USE IN THE CALCULATION OF THE MSCI INDEXES
FROM SOURCES WHICH MSCI CONSIDERS RELIABLE, NONE OF THE MSCI PARTIES WARRANTS OR GUARANTEES THE
ORIGINALITY, ACCURACY AND/OR THE COMPLETENESS OF ANY MSCI INDEX OR ANY DATA INCLUDED THEREIN. NONE OF THE
MSCI PARTIES MAKES ANY WARRANTY, EXPRESS OR IMPLIED, AS TO RESULTS TO BE OBTAINED BY LICENSEE, LICENSEE’S
CUSTOMERS OR COUNTERPARTIES, ISSUERS OF THE FUNDS, OWNERS OF THE FUNDS, OR ANY OTHER PERSON OR ENTITY,
FROM THE USE OF ANY MSCI INDEX OR ANY DATA INCLUDED THEREIN IN CONNECTION WITH THE RIGHTS LICENSED
HEREUNDER OR FOR ANY OTHER USE. NONE OF THE MSCI PARTIES SHALL HAVE ANY LIABILITY FOR ANY ERRORS, OMISSIONS
OR INTERRUPTIONS OF OR IN CONNECTION WITH ANY MSCI INDEX OR ANY DATA INCLUDED THEREIN. FURTHER, NONE OF THE
MSCI PARTIES MAKES ANY EXPRESS OR IMPLIED WARRANTIES OF ANY KIND, AND THE MSCI PARTIES HEREBY EXPRESSLY
DISCLAIM ALL WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, WITH RESPECT TO ANY MSCI
INDEX AND ANY DATA INCLUDED THEREIN. WITHOUT LIMITING ANY OF THE FOREGOING, IN NO EVENT SHALL ANY OF THE
MSCI PARTIES HAVE ANY LIABILITY FOR ANY DIRECT, INDIRECT, SPECIAL, PUNITIVE, CONSEQUENTIAL OR ANY OTHER DAMAGES
(INCLUDING WITHOUT LIMITATION LOST PROFITS) EVEN IF NOTIFIED OF THE POSSIBILITY OF SUCH DAMAGES.

© 2011 The Vanguard Group, Inc. All rights reserved.
Vanguard Marketing Corporation, Distributor.
	SPI 859 092011