His first novel, published at the age of 40 when he was teaching at the University of Texas, was "The Eiger Sanction", a thriller that became a worldwide best seller. In 1975, it was adapted as a movie directed by and starring Clint Eastwood. Trevanian described the movie as "vapid" in a footnote in his later novel "Shibumi". He requested (and received) a screenwriting credit as Rod Whitaker. The balance of the script was written by Warren Murphy, the mystery writer perhaps best known for co-writing the "Destroyer" series of action novels.