Silliphant worked steadily in TV through the 1990s, producing and writing the series "Route 66" (CBS, 1960-64) and "Longstreet" (ABC, 1971-72). He also produced many TV-movies and miniseries, including "The New Healers" (ABC, 1972), the horror tale "Salem's Lot" (CBS, 1979), the war drama "Fly Away Home" (ABC, 1981), "Mussolini: The Untold Story" (NBC, 1985), and the spy dramas "The Brotherhood of the Rose" (NBC, 1989) and "Day of Reckoning" (NBC, 1994).
In 1953, Silliphant made his big-screen debut producing and writing "The Joe Louis Story". He freelanced for large and small studios and after producing and writing a number of crime and action films, he had his first classic with the sci-fi thriller "Village of the Damned" (screenplay, 1960), the eerie story of alien children. Silliphant won a Best Screenplay Oscar for the tense racial drama, "In the Heat of the Night" (1967), and was lauded for his adaptations of "Charly" (1968), "Marlowe" (1969) "The New Centurions" (1972), and "The Killer Elite" (1975).
Some of his work was classic in another sense: Silliphant worked on such popular, high-camp films as "Shaft" (producer, 1971), as well as its sequels, and provided the screenplays for the disaster flicks, "The Poseidon Adventure" (1972), "The Towering Inferno" (1974) and "The Swarm" (1978) and the Sylvester Stallone arm-wrestling epic "Over the Top" (1987).
After a nine-year absence, Silliphant returned to features with his adaptation (co-written with Kirk Ellis) of Truman Capote's autobiographical novel "The Grass Harp" (1995). Directed by Charles Matthau and starring Piper Laurie and Sissy Spacek, the film is a gentle comedy about a young boy sent to live with his eccentric aunts. He has also contributed to the screenplay for Irvin Kershner's remake of the sci-fi classic "Forbidden Planet" (scheduled for release in 1996).