Korn/Ferry International Inc. (NYSE: KFY) ranked as the largest U.S. retained search firm with estimated 2011 U.S. retained search revenue of $364 million, according to the new list of largest retained search firms released by Staffing Industry Analysts.

Heidrick & Struggles International Inc. (NASD: HSII) ranked as the second-largest U.S. retained search firm with estimated U.S. retained search revenue of $248 million in 2011. Eight firms generated at least $25 million in U.S. retained search revenue in 2011.

Corporate members of Staffing Industry Analysts can download the list of largest U.S. retained search firms by clicking here.

Lists of largest direct hire firms and outplacement firms have also been released.

Robert Half International Inc. (NYSE: RHI) is the largest U.S. provider of direct hire with 2011 U.S. revenue of $206 million in this segment. Randstad ranked second with $84 million in U.S. direct hire revenue in 2011. Overall, seven firms posted at least $25 million in U.S. direct hire revenue in 2011.

Corporate members of Staffing Industry Analysts can download the list of largest U.S. direct hire providers by clicking here.

Among outplacement firms, Lee Hecht Harrison, the outplacement business of Adecco SA, ranked as the largest with U.S. outplacement revenue of $180 million in 2011. Only two firms generated at least $100 million in U.S. outplacement revenue in 2011.

Corporate members of Staffing Industry Analysts can download the list of largest U.S. outplacement providers by clicking here.