[SHIP LOGO VANGUARD/(R)/]


                                                                   P.O. Box 2600
                                                                 Valley Forge,PA
                                                                      19482-2600

                                                                    610-669-1538
                                                      Judy_L_Gaines@vanguard.com

October 17, 2007


Christian Sandoe, Esq.
U.S. Securities & Exchange Commission                    via electronic filing
100 F Street, N.E.
Washington, DC  20549

RE:      VANGUARD BOND INDEX FUNDS

Dear Mr. Sandoe,

     The  following  summarizes  our  discussion  of  this  afternoon  regarding
comments  to  Post-effective  Amendment  No. 46 of  Vanguard  Bond Index  Funds'
registration  statement.  The  Post-Effective  Amendment was filed on August 30,
2007. The comments pertain to Vanguard Inflation-Protected Securities Fund.


COMMENT 1:        PROSPECTUS - PRIMARY RISKS
- ----------------------------------------------------
COMMENT:   Since  the  Fund's  Primary  Investment   Strategies   reference
     investment  in  corporations,  credit  risk  should be  included in Primary
     Risks.


RESPONSE:  The  Fund invests in  inflation-indexed  bonds issued "by the U.S.
     government, its agencies and instrumentalities,  and corporations," meaning
     corporations of the U.S. government,  rather than "business"  corporations.
     Examples of the government  corporations in which the Fund invests are FNMA
     and GNMA. Per the Fund's most recent semiannual report, 99.8% of the Fund's
     assets were invested in U.S. Treasury Inflation-Indexed notes, and the Fund
     had an average  credit  quality of Aaa.  For all of these  reasons,  we are
     satisfied that we currently  disclose the relevant  primary  risks,  and we
     plan to leave the current disclosure unchanged.

COMMENT 2:        PROSPECTUS - FINANCIAL INFORMATION
- ----------------------------------------------------

COMMENT:   Will Vanguard's 485(b) filing include updated financials?

RESPONSE:  Yes, our 485(b) filing will include updated financials.

COMMENT 3:        PROSPECTUS - PLAIN TALK ABOUT THE FUND'S PORTFOLIO MANAGERS
- ------------------------------------------------------------------------------

COMMENT:   If the Fund has more than one Portfolio  Manager,  please specify
     the role played by each in managing the Fund's assets.

RESPONSE:  We  have discussed the comment with the Portfolio  Managers of the
     Fund, and they have confirmed that the existing  disclosure whereby the PMs
     are referred to as "co-managers" is an accurate description of their roles.
     The PMs work together in managing fund assets, sharing in the determination
     of strategies and risk exposures, and placing trades on behalf of the Fund.
     Furthermore,   we  believe  that  our  existing  disclosure  satisfies  the
     requirements of Item 5(a)(2) of Form N-1A.  Accordingly,  we do not plan to
     amend the disclosure.

COMMENT 4:        SAI - PORTFOLIO TRANSACTIONS
- ----------------------------------------------
COMMENT:   Please edit the first  sentence in the second full  paragraph  on
     Page B-39 to  clarify  which  funds did not pay any  brokerage  commissions
     during their past three fiscal years.
RESPONSE:  We will edit the sentence as requested.

COMMENT 5:        TANDY REQUIREMENTS
- ------------------------------------
As required by the SEC, the Fund acknowledges that:

o    The 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    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
Securities Regulation, Legal Department