Films:
* Caligula (1979): Arguably his most famous role, playing the sadistic Roman emperor's advisor, "Sextus".
* The Godfather: Part III (1990): Playing "Joey Zasa", a powerful and ruthless mobster.
* The Last American Virgin (1982): Playing a sleazy, manipulative older man named "The Duke".
* Tenebrae (1982): Playing a journalist who becomes a suspect in a series of brutal murders.
* Cannibal Holocaust (1980): Playing "Mark", a documentary filmmaker who goes on a journey to the Amazon rainforest.
* The Tenant (1976): Playing the role of a "policeman", though the film itself is largely considered a surreal and experimental work.
* The Night Porter (1974): Playing a former Nazi concentration camp guard, though it's worth noting that Steiner has disputed his involvement in the film, claiming he only appeared as a background extra.
* The Wicker Man (1973): Playing a minor character in this folk horror classic.
Television:
* Miami Vice (1984-1989): Playing a variety of roles, including a crime boss and a mobster.
* Hill Street Blues (1981-1987): Playing a drug dealer and a hitman in separate episodes.
* The Twilight Zone (1985-1989): Playing "The Usher" in the episode "The Afterlife".
* Night Court (1984-1992): Playing a character named "Vincent".
* The A-Team (1983-1987): Playing a villainous arms dealer.
John Steiner has also appeared in various other films and television shows, often in smaller roles or cameos. His filmography is diverse, spanning genres from horror and thriller to drama and comedy.
It's worth noting that while Steiner is known for his roles in exploitation films, he has also worked in mainstream projects. He is a versatile actor with a unique screen presence that has made him a memorable figure in cinema.