P.O. Box 2600

                                                                                                                                                                      Valley Forge, PA 19482-2600

                                                                                                                                                                      610-669-1538

                                                                                                                                                                      Judy_L_Gaines@vanguard.com

August 9, 2010

Christian Sandoe, Esq.

U.S. Securities & Exchange Commission                                   via electronic filing

100 F Street, N.E.

Washington, DC  20549

RE:       Vanguard Index Funds; File No. 2-56846

Dear Mr. Sandoe,

The following responds to your comments of August 6, 2010 on the post-effective amendment of the registration statement of the above-referenced registrant.  You commented on Post-Effective Amendment No. 117 that was filed on June 25, 2010 pursuant to Rule 485(a).  The following comments apply to the Vanguard 500 ETF.

Comment 1:    Fees and Expenses

Comment:         The Fund’s estimated annual operating expense ratio is provided without a breakdown of the management and other expenses. 

Response:         The estimated annual operating expense ratio will be provided, along with the breakdown of the management and other expenses, in a subsequent filing before the Fund goes effective. 

Comment 2:    Primary Investment Strategies

Comment:         Include the market capitalization strategy for the Fund.

Response:         The Item 9 disclosure includes the Fund’s asset-weighted median market capitalization.  We consider this placement to be sufficient and appropriate.

Comment 3:    Primary Risks

Comment:         Consider adding small and/or mid-cap risk to the primary investment strategy
disclosure.

Response:         This Fund will invest predominantly in large-cap stocks, and will track an index with a weighted average market cap of $75.2 billion as of June 30, 2010.  Accordingly, we do not consider the Fund’s minimal exposure to small- and mid-cap stocks to warrant discussion in the primary risk section.     

Comment 4:    Primary Risks

Comment:         Unless the Fund is advised by or sold through an insured depository institution, delete the sentence stating that “an investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the [FDIC] or any other governmental agency.”

Response:         The Fund may be sold through depository institutions.  Therefore, we will retain this disclosure.

Comment 5:    Tax Information

Comment:         Delete all but the first sentence of this section, which states that the Fund’s distributions may be taxed as ordinary income or capital gain.

Response:         We will make the requested edit.

Comment 6:    SAI­– Fundamental Policies

Comment:         The second to last paragraph of the fundamental policies section states that “unless otherwise required by the 1940 Act, if a percentage restriction is adhered to at the time the investment is made, a later change in the percentage resulting from a change in the market value of assets will not constitute a violation of the restriction.”  Please modify the disclosure to note that a fund’s borrowing is an exception to the general rule stated above.

Response:         We have modified the disclosure as requested.

Comment 7:    Tandy Requirements

As required by the SEC, the Fund acknowledges that:

·The Fund is responsible for the adequacy and accuracy of the disclosure in the filing.

·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.

·The 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