June 17, 2008


 Securities and Exchange Commission
 100 F Street NE
 Washington D.C. 20549


               Re: Van Kampen Unit Trusts, Series 778 (the "Fund")
                        (SEC# 333-150557) (CIK# 1402931)
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Ladies/Gentlemen:

         Transmitted herewith on behalf of Van Kampen Funds Inc. (the
"Sponsor"), depositor, sponsor and principal underwriter of the Fund, is
Amendment No.2 to the Registration Statement on Form S-6 for the registration
under the Securities Act of 1933 of units representing the ownership of
interests in the Fund. The Fund consists of one underlying unit investment
trust, Balanced Market Allocation Strategy 2008-2 (the "Portfolio"), which will
invest in exchange-traded funds ("ETFs") and common stocks.1 The Registration
Statement on Form S-6 relating to the subject Fund was initially filed with the
Securities and Exchange Commission (the "Commission") on May 1, 2008 and was
first amended on June 5, 2008. We received additional comments from the staff of
the Commission in a telephone conversation between Vincent J. Di Stefano of the
Commission and Mark Kneedy of our firm on June 16, 2008. This letter responds to
those comments.

COMMENTS

         The staff requested that the prospectus provide disclosure with respect
to the Fund's investment in emerging markets, value-style securities and
growth-style securities in the "Principle Risks".

RESPONSE

         Revisions have been made to page 5 in accordance with the staff's
comments.

         We have been advised that the Sponsor would like to be able to create
the Fund and have the Registration Statement declared effective by the
Commission on June 24, 2008.

         If you have any questions, please do not hesitate to contact Scott R.
Anderson at (312) 845-3834 or the undersigned at (312) 845-3787.

                                                               Very truly yours,

                                                          CHAPMAN AND CUTLER LLP

                                                          By ___________________
                                                                  Mark J. Kneedy


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     1    The Portfolio's investment in the underlying funds will be made in
          reliance on an order of the Commission pursuant to Section 12(d)(1)(J)
          of the Investment Company Act of 1940 (the "Act") exempting series of
          the Fund and its depositor, Van Kampen Funds Inc., from the provisions
          of Section 12(d)(1)(A), (B) and (C) of the Act to the extent necessary
          to permit trusts to acquire shares of registered investment companies
          and to permit such investment companies to sell such shares to a trust
          in excess of the percentage limitations set forth therein. Van Kampen
          Funds Inc. and Van Kampen Focus Portfolios, Investment Company Act
          Rel. Nos. 24548 (June 29, 2000) (notice) and 24566 (July 25, 2000)
          (order).