James Stewart had difficulty saying his lines on time due to hearing and possibly memory problems. Some of the cast were shocked by his aged appearance. Robert Mitchum recalled, "The picture was all about corpses, but Jimmy looked deader than any of them." Stewart actually outlived Mitchum by one day, nearly 20 years later.
James Stewart originally turned down the role of Gen. Sternwood, as he felt that since the movie was being relocated to England, a British actor should play the part.
According to Michael Winner, Robert Mitchum and Richard Boone were very drunk when they filmed the final shootout. Winner quipped that it should have been called "Gunfight at Alcoholics Anonymous."