Vanguard Mega Cap 300 Index Fund

Supplement to the Prospectus and Summary Prospectus

New Target Index

The board of trustees of Vanguard Mega Cap 300 Index Fund has approved the adoption of the CRSP US Mega Cap Index as the new target index for the Fund, replacing the MSCI US Large Cap 300 Index. The board believes that the new index is well-constructed and offers comprehensive coverage of the Fund’s market segment. In addition, Vanguard’s agreement with the new index provider may result in considerable savings to shareholders over time in the form of lower expense ratios.

The Fund is expected to implement the index change sometime over the coming months. To protect the Fund from the potential for harmful “front running” by traders, the exact timing of the index change and portfolio transition will not be disclosed to investors. In the meantime, the Fund will continue seeking to track its current index.

The new index measures the same market segment as the current index, so the investment objective and risks described in the Fund’s current prospectus will not change. The Fund’s new target index could provide different investment returns (either lower or higher) or different levels of volatility than its existing index over any period of time.

The adjustments to the Fund’s portfolio holdings are expected to result in modest, temporary increases in the Fund’s transaction costs and turnover rate. The transition also may cause the Fund to realize taxable capital gains, although the board of trustees believes that any gains realized are likely to be offset by accumulated tax losses. It is important to note that the actual transaction costs, turnover rate, and capital gains will be highly dependent upon a number of factors, including the market environment at the time of the portfolio adjustments.

Additional information about the new target index is available on vanguard.com.

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Fund Name Change
Vanguard Mega Cap 300 Index Fund will change its name to Vanguard Mega
Cap Index Fund to better coincide with its new target index. The name change
will occur at the same time that the index change becomes effective.
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.
Vanguard funds are not sponsored, endorsed, sold, or promoted by the University of Chicago or its Center for Research in
Securities Prices, and neither the University of Chicago nor its Center for Research in Securities Prices makes any
representation regarding the advisability of investing in the funds.
© 2012 The Vanguard Group, Inc. All rights reserved.
Vanguard Marketing Corporation, Distributor.	PSI 828A 102012

Vanguard Mega Cap 300 Value Index Fund
Vanguard Mega Cap 300 Growth Index Fund
Supplement to the Prospectus and Summary Prospectuses
New Target Indexes
The board of trustees of Vanguard Mega Cap 300 Value Index Fund and
Vanguard Mega Cap 300 Growth Index Fund has approved the adoption of new
target indexes for each Fund. The board believes that the new indexes, listed
below, are well-constructed and offer comprehensive coverage of the Funds’
respective market segments. In addition, Vanguard’s agreement with the new
index provider may result in considerable savings to shareholders over time in
the form of lower expense ratios.
Vanguard Fund	Current Target Index	New Target Index
Mega Cap 300 Value	MSCI US Large Cap	CRSP US Mega Cap
Index Fund	Value Index	Value Index
Mega Cap 300 Growth	MSCI US Large Cap	CRSP US Mega Cap
Index Fund	Growth Index	Growth Index
The Funds are expected to implement these changes sometime over the
coming months. To protect the Funds from the potential for harmful “front
running” by traders, the exact timing of the index changes and portfolio
transitions will not be disclosed to investors. In the meantime, the Funds will
continue seeking to track their current indexes.
Each new index measures the same market segment as the corresponding
current index, so the investment objectives and risks described in each Fund’s
current prospectus will not change. A Fund’s new target index could provide
different investment returns (either lower or higher) or different levels of volatility
than its existing index over any period of time.
The adjustments to each Fund’s portfolio holdings are expected to result in
modest, temporary increases in the Fund’s transaction costs and turnover rate. The
transition also may cause each Fund to realize taxable capital gains, although the
board of trustees believes that any gains realized are likely to be offset by

(over, please)

accumulated tax losses. It is important to note that the actual transaction costs,
turnover rate, and capital gains will be highly dependent upon a number of factors,
including the market environment at the time of the portfolio adjustments.
Additional information about the new target indexes is available on vanguard.com.
Fund Name Changes
To better coincide with their new target indexes, Vanguard Mega Cap 300 Value
Index Fund will change its name to Vanguard Mega Cap Value Index Fund, and
Vanguard Mega Cap 300 Growth Index Fund will change its name to Vanguard
Mega Cap Growth Index Fund. The name changes will occur at the same time
that the index changes become effective.
THESE FUNDS ARE 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 THESE FUNDS OR ANY MEMBER OF THE PUBLIC REGARDING THE ADVISABILITY OF
INVESTING IN FUNDS GENERALLY OR IN THESE FUNDS 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 THESE FUNDS OR THE ISSUER OR
OWNER OF THESE FUNDS. NONE OF THE MSCI PARTIES HAS ANY OBLIGATION TO TAKE THE NEEDS OF THE
ISSUERS OR OWNERS OF THESE FUNDS 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 THESE FUNDS TO BE ISSUED OR IN THE
DETERMINATION OR CALCULATION OF THE CONSIDERATION INTO WHICH THESE FUNDS ARE REDEEMABLE.
NONE OF THE MSCI PARTIES HAS ANY OBLIGATION OR LIABILITY TO THE OWNERS OF THESE FUNDS IN
CONNECTION WITH THE ADMINISTRATION, MARKETING OR OFFERING OF THESE FUNDS.
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.
Vanguard funds are not sponsored, endorsed, sold, or promoted by the University of Chicago or its Center for Research in
Securities Prices, and neither the University of Chicago nor its Center for Research in Securities Prices makes any
representation regarding the advisability of investing in the funds.
© 2012 The Vanguard Group, Inc. All rights reserved.
Vanguard Marketing Corporation, Distributor.	PSI 828B 102012