Though he also worked as an actor and director, Mr. Kass was best known for his work as an acting instructor who relentlessly pushed his students toward greater authenticity in their performances. Among his hundreds of students were Olympia Dukakis, John Cazale and Val Kilmer. He was a master-acting teacher from 1956 to 1960 at Boston University and served the same position at the NYU School of the Arts 1965 to 82.

Born in Brooklyn on April 28, 1923, Mr. Kass began as a protégé of Clifford Odets, who asked him to direct the first staging of his play The Country Girl at the Lakes Region Playhouse in New Hampshire. When the drama came to Broadway, Odets took over the directing duties, but cast Mr. Kass in the role of the playwright in the backstage story.

Mr. Kass' other acting credits included the American premiere of Jean-Paul Sartre's No Exit, in which he played the bellboy; the Elia Kazan-staged Jacobowsky and the Colonel, Skipper Next to God and The Innocent Voyage. He also directed four Broadway plays: a revival of Odets' Night Music; the 1964 production of Lorraine Hansberry's final play, The Sign in Sidney Brustein's Window; Postmark Zero, written by Hansberry's former husband, Robert Nemiroff; and Nathan Weinstein, Mystic, Connecticut.

Mr. Kass also directed commercials, winning two Clios. His single film, "Time of the Heathen," won grand prize in the Bergamo Film Festival.

He is survived by his wife of 60 years, Nance Robbins; his sons Sam and Robbie; and five grandchildren (including talent publicist Alana Kass).