Lee Marvin faked the recoil from the .44 Magnum when he shoots in Lynne's bed. These were in fact blanks, but afterward when shooting in Alcatraz they tried with real bullets and there was no recoil at all. Marvin said to director John Boorman, "Fiction overtakes reality".
During a rehearsal taking place in the home of Lee Marvin, he hit John Vernon so hard that it made Vernon cry.
This was the first major picture to film on location at Alcatraz Island after the closure of the federal prison in 1963.
When Walker, in Chris' company, switches on the TV at Brewster's house, the music you hear is the overture to Richard Wagner's "Die Meistersinger von Nürnberg"