 Korshak was highly successful in the field of labor consulting and negotiations, and his client list included Hilton Hotels, Hyatt Hotels, MGM, Playboy, MCA/Universal, and Diner's Club.One of his clients was Jimmy Hoffa, notorious head of the International Brotherhood of Teamsters; Korshak was heavily involved in the Teamsters' west coast operations during a time when organized labor was at the peak of its activity.Korshak was an attorney for various elements of the Chicago Outfit.