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Vanguard Mid-Cap Index Fund

Summary Prospectus

April 26, 2012

Investor Shares & Admiral™ Shares

Vanguard Mid-Cap Index Fund Investor Shares (VIMSX)

Vanguard Mid-Cap Index Fund Admiral Shares (VIMAX)

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

April 26, 2012, 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 800-662-7447 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 or Admiral Shares of the Fund.


Shareholder Fees
(Fees paid directly from your investment)
	Investor Shares	Admiral Shares
Sales Charge (Load) Imposed on Purchases	None	None
Purchase Fee	None	None
Sales Charge (Load) Imposed on Reinvested Dividends	None	None
Redemption Fee	None	None
Account Service Fee (for fund account balances below $10,000)	$20/year	$20/year


Annual Fund Operating Expenses
(Expenses that you pay each year as a percentage of the value of your investment)
	Investor Shares	Admiral Shares
Management Expenses	0.20%	0.08%
12b-1 Distribution Fee	None	None
Other Expenses	0.04%	0.02%
Total Annual Fund Operating Expenses	0.24%	0.10%

Examples

The following examples are intended to help you compare the cost of investing in the
Fund’s Investor Shares or Admiral Shares with the cost of investing in other mutual
funds. They illustrate the hypothetical expenses that you would incur over various
periods if you invest $10,000 in the Fund’s shares. These examples assume that the
Shares provide a return of 5% a year and that total annual fund 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
Investor Shares	$25	$77	$135	$306
Admiral Shares	$10	$32	$56	$128

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 more 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 examples, reduce the Fund’s performance.
During the most recent fiscal year, the Fund’s portfolio turnover rate was 22%.

Primary Investment Strategies
The Fund employs an indexing investment approach designed to track the
performance of the MSCI US Mid Cap 450 Index, a broadly diversified index of stocks
of mid-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, which could cause the Fund to underperform the
overall stock market.

• 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.

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 of the share classes presented
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 (before and after taxes) 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).


Average Annual Total Returns for Periods Ended December 31, 2011
	1 Year	5 Years	10 Years
Vanguard Mid-Cap Index Fund Investor Shares
Return Before Taxes	–2.11%	1.21%	6.60%
Return After Taxes on Distributions	–2.29	0.99	6.34
Return After Taxes on Distributions and Sale of Fund Shares	–1.16	0.98	5.72
Vanguard Mid-Cap Index Fund Admiral Shares
Return Before Taxes	–1.97%	1.34%	6.71%
Comparative Indexes
(reflect no deduction for fees, expenses, or taxes)
S&P MidCap 400 Index	–1.73%	3.32%	7.04%
Spliced Mid Cap Index	–1.91	1.37	6.70
MSCI US Mid Cap 450 Index	–1.91	1.37	6.86

Actual after-tax returns depend on your tax situation and may differ from those shown
in the preceding table. When after-tax returns are calculated, it is assumed that the
shareholder was in the highest individual federal marginal income tax bracket at the
time of each distribution of income or capital gains or upon redemption. State and
local income taxes are not reflected in the calculations. Please note that after-tax
returns are shown only for the Investor Shares and may differ for each share class.
After-tax returns are not relevant for a shareholder who holds fund shares in a tax-
deferred account, such as an individual retirement account or a 401(k) plan. Also,
figures captioned Return After Taxes on Distributions and Sale of Fund Shares will be
higher than other figures for the same period if a capital loss occurs upon redemption
and results in an assumed tax deduction for the shareholder.

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.

Purchase and Sale of Fund Shares
You may purchase or redeem shares online through our website (vanguard.com), by
mail (The Vanguard Group, P.O. Box 1110, Valley Forge, PA 19482-1110), or by telephone
(800-662-2739). The following table provides the Fund’s minimum initial and subsequent
investment requirements.


Account Minimums	Investor Shares	Admiral Shares
To open and maintain an account	$3,000	$10,000
To add to an existing account	Generally $100 (other than	Generally $100 (other than
	by Automatic Investment	by Automatic Investment
	Plan, which has no	Plan, which has no
	established minimum)	established minimum)

Tax Information
The Fund’s distributions may be taxable as ordinary income or capital gain.

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

Vanguard Mid-Cap Index Fund Admiral Shares—Fund Number 5859

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.

SP 859 042012