SecProbe.io

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                                  [SHIP LOGO]
                          [THE VANGUARD GROUP(R) LOGO]

                                                              October 28, 2005

Christian Sandoe, Esq.
Division of Investment Management
U.S. Securities and Exchange Commission    via electronic filing
450 Fifth Street,
N.W., Fifth Floor
Washington, D.C. 20549

                       Re: Vanguard Index Funds

Dear Mr. Sandoe:

 The following responds to your comments of October 28, 2005 on the post-
effective amendment of the registration statement of the above-referenced
registrant. You commented on Post-Effective Amendment No. 97 that was filed on
September 16, 2005.

Comment 1:        Cover Sheet
-----------------------------
Comment:          The cover sheet indicated that PEA No. 97 was a 485(b) filing.
                  This filing contained disclosure that rendered it ineligible
                  for a 485(b) filing.

Response:         The cover sheet contained a typo.  Our intention, as stated in
                  the cover letter that accompanied our filing, was to file PEA
                  No. 97 as a 485(a) filing.

Comment 2:        Cover Letter
------------------------------
Comment:          The paragraph regarding Rule 485(d)(2) requires some
                  modifications since it contains some technical inaccuracies.

Response:         We will make appropriate modifications to the cover letters
                  used for future filings.

Comment 3:        Prospectus - Primary Investment Strategies of Institutional
                  Total Stock Market Index Fund
-----------------------------------------------
Comment:          Since the MSCI US Broad Market Index includes mid- and small-
                  cap stocks, their risks should be disclosed in the risk/return
                  summary.

Response:         Since the MSCI US Broad Market Index, with a median market-cap
                  of approximately $27 billion, is dominated by large-cap
                  stocks, we do not consider the much lesser existence of the
                  mid- and small-cap stocks to warrant inclusion of this
                  disclosure in the primary investment strategies
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October 28, 2005
Christian Sandoe
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                  section. However, we will include a reference to the
                  Institutional Total Stock Market Index Fund where we discuss
                  the risks of mid- and small-cap stocks in the Item 4
                  disclosure.

Comment 4:        Risk of Nondiversification
--------------------------------------------
Comment:          Modify the final sentence in the paragraph so it clarifies
                  that these funds, while classified as nondiviersified, have
                  actually "operated as" (rather than "have been") diversified.

Response:         We will make the requested modification.

Comment 5:        Other Investment Policies and Risks
-----------------------------------------------------
Comment:          The prospectus states that each Fund may invest to a limited
                  extent in foreign securities.  As US stock index funds, are
                  there international holdings?

Response:         The funds do not intentionally invest in foreign stocks.
                  However, to the extent that a stock holding of one of the
                  funds is issued by a US company, and that company is part of a
                  merger or acquisition by or with a foreign company, the fund
                  may inadvertently wind up with a foreign holding. A fund would
                  only continue to hold such a security if it remains a holding
                  of the fund's target index.

Comment 6:        Frequent Trading or Market-Timing
---------------------------------------------------
Comment:          The Fund's broad policies with respect to frequent trading and
                  market-timing are disclosed on page 34 of the prospectus under
                  the heading "Frequent Trading or Market-Timing." However,
                  specific policies applicable to discrete types of investors
                  are disclosed in various places throughout the "Investing with
                  Vanguard" section. All of the Fund's policies concerning
                  frequent trading and market-timing should be disclosed
                  together under the heading "Frequent Trading and
                  Market-Timing."

Response:         We believe that the Fund's policies against frequent trading
                  and market-timing are properly disclosed in the prospectus
                  pursuant to Item 6(e)(4) of Form N-1A. Item 6(e)(4) does not
                  require that the specific policies applicable to each type of
                  shareholder be disclosed together in the prospectus. As such,
                  we believe that it is appropriate to have the general
                  discussion of the Fund's policies against frequent trading and
                  Market-timing under the heading "Frequent Trading or
                  Market-Timing" with a reference to the "Investing with
                  Vanguard" section where specific policies applicable to
                  different types of shareholders and transactions are
                  disclosed.

                  We believe that removing the disclosure from the "Investing
                  with Vanguard" section and combining the disclosure into a
                  single "Frequent Trading and Market-Timing" section would make
                  the discussion of transaction policies
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October 28, 2005
Christian Sandoe
Page 3 of 4

                  incomplete in the "Investing with Vanguard" section. Repeating
                  the specific policies in both the "Investing with Vanguard"
                  section and under the "Frequent Trading and Market-Timing"
                  heading would unnecessarily clutter the prospectus with
                  duplicative disclosure.

Comment 7:        Share Price
-----------------------------
Comment:          Describe the effects of fair value pricing.

Response:         We have reviewed our disclosure and think we already describe
                  the effects of fair value pricing.

                  In the Share Price section, we state that "[w]hen fair-value
                  pricing is employed, the prices of securities used by a fund
                  to calculate its NAV may differ from quoted or published
                  prices for the same securities." We think that is the primary
                  effect of using fair-value pricing.

                  Additionally, in the Frequent Trading or Market-Timing
                  section, we state that "Each fund (other than money market
                  funds), in determining its net asset value, will use
                  fair-value pricing as described in the Share Price section.
                  When used, fair-value pricing may reduce or eliminate the
                  profitability of certain frequent-trading strategies." We
                  think this is an additional possible effect of using
                  fair-value pricing.

                  We think the above disclosure addresses your comment, so we do
                  not plan to add anything.

Comment 8:        Converting Shares
-----------------------------------
Comment:          Better explain what self-directed conversions are.

Response:         A self-directed conversion is a conversion done at the
                  direction of the shareholder.  We do not think clarification
                  on this point is necessary and we are comfortable with our
                  existing disclosure.

Comment 9:        Frequent Trading Limits
-----------------------------------------
Comment:          The disclosure states that each Vanguard fund..."limits"
                  purchases or exchanges into a fund for 60 days after an
                  investor has redeemed or exchanged out of that fund. If by
                  "limit" we mean "refuse" we should clarify that point.

Response:         "Limits" accurately describes the policy since immediately
                  following the sentence in question, we list the situations
                  where we will allow purchases or exchanges into a fund during
                  the 60-day period. Since there are a handful of exceptions, we
                  are actually "limiting" rather than "refusing" purchases.
                  Accordingly, we do not plan to amend the sentence.
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October 28, 2005
Christian Sandoe
Page 4 of 4

Comment 10:       SAI - Description of PM Compensation
------------------------------------------------------
Comment:          Do the portfolio managers of these funds manage any funds
                  subject to performance fees?

Response:         No, these portfolio managers do not manage any funds subject
                  to performance fees.

Comment 11:       Tandy Requirements
------------------------------------
Comment:          The SEC is now requiring all registrants to provide at the end
                  of response letters to registration statement comments, the
                  following statements:
                  o Each Fund is responsible for the adequacy and accuracy of
                    the disclosure in the filing.
                  o Staff comments or changes in response to staff comments in
                    the filings reviewed by the staff do not foreclose the
                    Commission from taking any action with respect to the
                    filing.
                  o Each Fund may not assert staff comments as a defense in any
                    proceeding initiated by the Commission or any person under
                    the federal securities laws of the United States.

Response:         As required by the SEC, we will provide the foregoing
                  acknowledgements.

                                    * * * * *

              As required by the SEC, the Funds acknowledge that:

o Each Fund is responsible for the adequacy and accuracy of the disclosure in
  the filing.
o Staff comments or changes in response to staff comments in the filings
  reviewed by the staff do not foreclose the Commission from taking any action
  with respect to the filing.
o Each Fund may not assert staff comments as a defense in any proceeding
  initiated by the Commission or any person under the federal securities laws of
  the United States.

 Please contact me at (610) 669-1538 with any questions or comments
regarding the above responses. Thank you.

Sincerely,

Judith L. Gaines
Associate Counsel
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