William Blair Small Cap Growth Fund Class I

The fund normally invests at least 80% of its net assets in stocks of small capitalized ("small cap") companies. It invests primarily in a diversified portfolio of equity securities, including common stocks and other forms of equity investments, of small cap U.S. growth companies that are expected to exhibit quality growth characteristics. For purposes of the fund, the advisor considers a company to be a small cap company if it has a market capitalization no larger than the largest capitalized company included in the Russell 2000® Index at the time of the fund's investment.