<PAGE> PAGE 1
000 B000000 12/31/98
000 C000000 0000822632
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000 F000000 Y
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000 I000000 3.0.a
000 J000000 A
001 A000000 WILLIAM BLAIR & CO.
001 B000000 811-5344
001 C000000 3123648000
002 A000000 222 WEST ADAMS
002 B000000 CHICAGO
002 C000000 IL
002 D010000 60606
003 000000 N
004 000000 N
005 000000 N
006 000000 N
007 A000000 Y
007 B000000 6
007 C010100 1
007 C020100 GROWTH FUND
007 C030100 N
007 C010200 2
007 C020200 READY RESERVES FUND
007 C030200 N
007 C010300 3
007 C020300 INCOME FUND
007 C030300 N
007 C010400 4
007 C020400 INTERNATIONAL GROWTH FUND
007 C030400 N
007 C010500 5
007 C020500 VALUE DISCOVERY FUND
007 C030500 N
007 C010600 6
007 C020600 EMERGING MARKETS GROWTH FUND
007 C030600 N
007 C010700 7
007 C010800 8
007 C010900 9
007 C011000 10
077 A000000 Y
077 B000000 N
077 C000000 Y
077 D000000 N
077 E000000 N
077 F000000 N
077 G000000 N
<PAGE> PAGE 2
077 H000000 N
077 I000000 N
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SIGNATURE TERENCE M. SULLIVAN
TITLE VICE PRESIDENT
EXHIBIT 99.77B
William Blair Mutual Funds, Inc.
222 West Adams Street
Chicago, Illinois 60606
(312) 364-8000
Supplement to the Prospectus
dated May 1, 1998
The following information replaces the disclosure regarding the Value Discovery
Fund on page 12 of the Prospectus in the section entitled "Value Discovery
Fund - Portfolio Securities."
The portfolio may invest up to 15% of its net assets in foreign securities,
which may include American Depository Receipts or substantially similar
investments; however, the portfolio may invest only up to 5% of its net
assets directly in foreign securities.
The following information replaces the first sentence of the disclosure
regarding the Value Discovery Fund on page 41 entitled "Investment
Glossary - Real Estate Investment Trusts."
The Value Discovery Fund may invest without limit in real estate investment
trusts.
Supplement dated November 10, 1998
