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Vanguard PRIMECAP Fund

Summary Prospectus

January 28, 2013

Admiral™ Shares for Participants

Vanguard PRIMECAP Fund Admiral Shares (VPMAX)

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

January 28, 2013, 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 provide long-term capital appreciation.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Admiral 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 (on shares held less than one year)	None

Annual Fund Operating Expenses

(Expenses that you pay each year as a percentage of the value of your investment)


Management Expenses	0.34%
12b-1 Distribution Fee	None
Other Expenses	0.02%
Total Annual Fund Operating Expenses	0.36%

Example

The following example is intended to help you compare the cost of investing in the Fund’s Admiral 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 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
$37	$116	$202	$456

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 example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 6%.

Primary Investment Strategies

The Fund invests in stocks considered to have above-average earnings growth potential that is not reflected in their current market prices. The Fund’s portfolio consists predominantly of large- and mid-capitalization stocks.

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 is subject to the following risks, which
could affect the Fund’s performance:

• 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.

• Asset concentration risk, which is the chance that the Fund’s performance may be
adversely affected by the poor performance of relatively few stocks as compared with
other mutual funds. The Fund tends to invest a high percentage of its assets in its top
ten holdings.

• Investment style risk, which is the chance that returns from large- and mid-
capitalization growth stocks will trail returns from the overall stock market. Large- and
mid-cap stocks each tend to go through cycles of doing better—or worse—than other
segments of the stock market or the stock market in general. These periods have, in
the past, lasted for as long as several years. Historically, mid-cap stocks have been
more volatile in price than large-cap stocks.

• Manager risk, which is the chance that poor security selection or focus on securities in
a particular sector, category, or group of companies will cause the Fund to underperform

relevant benchmarks or other funds with a similar investment objective. Significant investments in the health care and information technology sectors subject the Fund to proportionately higher exposure to the risks of these sectors.

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 Admiral 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 a relevant market index, which has 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 PRIMECAP Fund Admiral Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 16.93% (quarter ended June 30, 2003), and the lowest return for a quarter was –22.38% (quarter ended December 31, 2008).


Average Annual Total Returns for Periods Ended December 31, 2012
	1 Year	5 Years	10 Years
Vanguard PRIMECAP Fund Admiral Shares	15.38%	3.13%	10.03%
Standard & Poor's 500 Index
(reflects no deduction for fees or expenses)	16.00%	1.66%	7.10%

Investment Advisor
PRIMECAP Management Company

Portfolio Managers

Theo A. Kolokotrones, Vice Chairman of PRIMECAP. He has co-managed the Fund since 1985.

Joel P. Fried, President of PRIMECAP. He has co-managed the Fund since 1988.

Mitchell J. Milias, Chairman of PRIMECAP. He has co-managed the Fund since 2002.

Alfred W. Mordecai, Executive Vice President of PRIMECAP. He has co-managed the Fund since 1999.

M. Mohsin Ansari, Senior Vice President of PRIMECAP. He has co-managed the Fund since 2007.

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 PRIMECAP Fund Admiral Shares—Fund Number 559

SPI 559 012013