Mr. Williams, who was a co-founder of the New Federal Theatre, starred in a string of dramas on Broadway in the early and mid-1970s. His first appearance, in 1970, was in filmmaker Melvin van Peebles' unorthodox musical assemblage, Ain't Supposed to Die a Natural Death. His next two assignments, What the Wine-Sellers Buy and Black Picture Show—both New York Shakespeare Festival productions staged at Lincoln Center—were short-lived, but brought Mr. Williams a Tony nomination and Drama Desk Award nomination apiece. He won the Drama Desk for Wine-Sellers, in which he played a Detroit pimp called Rico.

"Mr. Williams is cool and brilliant," wrote Clive Barnes in the New York Times of Wine-Sellers, "like a refrigerated diamond."

We Interrupt This Program… and The Poison Tree followed in 1975 and 1976. Following those plays, Mr. Williams concentrated on film work, taking parts in "Dog Day Afternoon," "The Deep," "The Jerk," "Gardens of Stone," "Tap," "Mo' Better Blues," "Edward Scissorhands," and numerous television movies and guest shots on television series. As on stage, his most memorable filmic role was as a pimp, in this case a flamboyant philosopher armed with a sword cane called Pretty Tony in the 1973 blaxploitation film "The Mack."

Mr. Williams was sometimes frustrated by the lack of opportunities African-American actors faced in Hollywood. "Too much of this business is run on favors," he told the New York Times in 1980. "But there are so few black executives that black actors have no access to the system."

"Producers don't think about casting a black unless the script says 'black,'" he added. Mr. Williams was born Aug. 9, 1934, in Chicago, and suffered from polio as a child. He first made a splash Off-Broadway in 1968 in Big Time Buck White, which he also directed. In 1970, he directed Ed Bullins' The Pig Pen.