1
                                                                  EXHIBIT (a)(6)

                      Supplement dated May 8, 2000 to the

                    Offer to Purchase, dated April 20, 2000
                                      and
                  Letter of Transmittal, dated April 20, 2000

     The Offer to Purchase, the Letter of Transmittal and ancillary offer
documents of the Van Kampen Senior Floating Rate Fund (the "Trust") are hereby
supplemented to state that the Trust is offering to purchase up to 54,534,630
of its Common Shares pursuant to the terms of the Offer. Terms not defined in
this supplement shall have the same meanings as defined in the Offer to
Purchase and Letter of Transmittal. All references to the number of Common
Shares subject to the Offer should be changed to 54,534,630. The cost of
purchasing the full 54,534,630 Common Shares pursuant to the Offer would be
approximately $532,803,335 (assuming an NAV of $9.77 per Common Share on the
Expiration Date). If more than 54,534,630 Common Shares are duly tendered prior
to the expiration of the Offer, the Trust presently intends to, assuming no
changes in the factors originally considered by the Board of Trustees when it
determined to make the Offer and the other conditions set forth in the Offer,
but is not obligated to, extend the Offer period, if necessary, and increase
the number of Common Shares that the Trust is offering to purchase to an amount
which it believes will be sufficient to accommodate the excess Common Shares
tendered as well as any Common Shares tendered during the extended Offer period
or purchase 54,534,630 Common Shares (or such greater number of Common Shares
sought) on a pro rata basis.