SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 ---------- SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULE 13d-1(b)(c), AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13d-2(b) (Amendment No. __)(1) Acxiom Corporation - -------------------------------------------------------------------------------- (Name of Issuer) Common - -------------------------------------------------------------------------------- (Title of Class of Securities) 005125109 - -------------------------------------------------------------------------------- (CUSIP Number) December 31, 1999 - -------------------------------------------------------------------------------- (Date of Event which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: |x_| Rule 13d-1 (b) |_| Rule 13d-1 (c) |_| Rule 13d-1 (d) - ---------- (1) The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page. The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).CUSIP No. SCHEDULE 13G Page _ of __ Pages - -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY) William Blair & Company, L.L.C. 36-2214610 - -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) |_| (b) |_| - -------------------------------------------------------------------------------- 3 SEC USE ONLY - -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Chicago, Illinois USA - -------------------------------------------------------------------------------- 5 SOLE VOTING POWER 2,232,589 -------------------------------------------------------------- NUMBER OF 6 SHARED VOTING POWER SHARES BENEFICIALLY OWNED BY -------------------------------------------------------------- EACH 7 SOLE DISPOSITIVE POWER REPORTING PERSON 6,493,291 WITH -------------------------------------------------------------- 8 SHARED DISPOSITIVE POWER - -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 6,493,291 - -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* |_| - -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 7.6% - -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* BD, IA - -------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT!