RULE 497 DOCUMENT

On behalf of William Blair Emerging Leaders Growth Fund and William Blair Global Growth Fund, each a series of William Blair Funds (the “Funds”), and pursuant to Rule 497(e) under the Securities Act of 1933, as amended (the “Securities Act”), the purpose of this filing is to submit an interactive data file in the manner provided by Rule 405 of Regulation S-T and General Instruction C.3(g) of Form N-1A. The interactive data file included as an exhibit to this filing relates to the supplement filed with the Securities and Exchange Commission on behalf of the Funds pursuant to Rule 497(e) under the Securities Act on December 10, 2012; such supplement (accession number 0001193125-12-497008) is incorporated by reference into this Rule 497 Document.