WILLIAM BLAIR FUNDS
CLASS A SHARES
CLASS B SHARES
CLASS C SHARES
CLASS I SHARES
CLASS N SHARES
SUPPLEMENT TO PROSPECTUSES DATED DECEMBER 22, 1999
The Board of Trustees approved a change to the operating policies of the
Income Fund on February 15, 2000 to permit up to 10% of the Fund's total assets
to be invested in debt securities with a long term rating of "BBB-" or above. To
reflect this change, the full paragraph following the caption "Additional
Strategies" on page 35 of the Class N Shares prospectus and page 40 of the Class
A, B, C, and I Shares prospectus with regard to the Income Fund is hereby
amended to read as follows:
"Up to 10% of the Fund's total assets may be invested in (1) unrated debt
securities, provided that the Adviser deems such securities to be of at
least "A-" quality and provided that the comparable debt of the issuer has
a rating of at least "A-" or its equivalent by one of the four Ratings
Organizations; or (2) debt securities which are rated "BBB-" (or its
equivalent) or better by each Rating Organization by which such securities
are rated, so long as the Fund does not invest more than 3% of its total
net assets in securities of any single issuer whose securities are rated
"BBB-" and, in the event that a security held by the Fund is downgraded
below "BBB-" (or its equivalent) by a Rating Organization, the Fund will
sell the security within 90 days; or (3) a combination of such unrated and
"BBB-" rated debt securities. Debt securities rated "BBB" or below are
considered to be investment grade, they may have speculative
characteristics, and changes in economic conditions or other circumstances
are more likely to lead to a weakened capacity to make principal and
interest payments than is the case for higher grade bonds."
February 18, 2000
William Blair Funds
222 West Adams Street
Chicago, Illinois 60606
