Form 497K VANGUARD INSTITUTIONAL

Investment Objective

The Fund seeks to track the performance of a benchmark index that measures the investment return of the overall stock market.

Fees and Expenses

The following table describes the fees and expenses you may pay if you buy and hold Institutional Shares or Institutional Plus Shares of the Fund.

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Examples

The following examples are intended to help you compare the cost of investing in the Fund’s Institutional Shares or Institutional Plus Shares with the cost of investing in other mutual funds. They illustrate the hypothetical expenses that you would incur over various periods if you invested $10,000 in the Fund’s shares. These examples assume that the Shares provide a return of 5% each year and that total annual fund operating expenses remain as stated in the preceding table. You would incur these hypothetical expenses 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:

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 9% of the average value of its portfolio.

Principal Investment Strategies

The Fund employs an indexing investment approach designed to track the performance of the CRSP US Total Market Index, which represents approximately 100% of the investable U.S. stock market and includes large-, mid-, small-, and micro-cap stocks regularly traded on the New York Stock Exchange and Nasdaq. 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 characteristics. These key characteristics include industry weightings and market capitalization, as well as certain financial measures such as price/earnings ratio and dividend yield.

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Principal 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. 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. In addition, the Fund’s target index may, at times, become focused in stocks of a particular market sector, which would subject the Fund to proportionately higher exposure to the risks of that sector.

• 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 Institutional 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 Institutional Total Stock Market Index Fund Institutional Shares

During the periods shown in the bar chart, the highest return for a calendar quarter was 16.96% (quarter ended June 30, 2009), and the lowest return for a quarter was –22.65% (quarter ended December 31, 2008).

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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 Institutional 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 may 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. (Vanguard)

Portfolio Managers

Walter Nejman, Portfolio Manager at Vanguard. He has co-managed the Fund since 2016.

Gerard C. O’Reilly, Principal of Vanguard. He has co-managed the Fund since 2016.

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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 minimum investment amount required to open and maintain a Fund account for Institutional Shares or Institutional Plus Shares is $100 million or $200 million, respectively. The minimum investment amount required to add to an existing Fund account is generally $1.

Tax Information

The Fund’s distributions may be taxable as ordinary income or capital gain. If you are investing through a tax-deferred retirement account, such as an IRA, special tax rules apply.

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 Institutional Total Stock Market Index Fund Institutional Shares—Fund Number 870 Vanguard Institutional Total Stock Market Index Fund Institutional Plus Shares—Fund Number 871

Vanguard funds are not sponsored, endorsed, sold, or promoted by the University of Chicago or its Center for Research in Security Prices, and neither the University of Chicago nor its Center for Research in Security Prices makes any representation regarding the advisability of investing in the funds.

© 2016 The Vanguard Group, Inc. All rights reserved.
Vanguard Marketing Corporation, Distributor.

SPI 870 042016