William Bast was born and raised in Milwaukee, Wisconsin. After graduating from high school, he spent his first year as an undergraduate in pre-law at the University of Wisconsin, then transfered to UCLA in Los Angeles where he changed his study course to Theater Arts.
In 1950, he met and befriended another UCLA Theater Arts student, James Dean, with whom he shared living quarters while at UCLA. During the five years that followed, while living in Los Angeles and New York together, the two young men pursued their professional careers, Bast as a writer, Dean as an actor.
Upon Dean's untimely death in 1955, Bast chronicled their friendship in his book, "James Dean: a biography," published by Ballantine Books in 1956. From that time until today, he has written feature films and written and produced some 200 hours of primetime television.