Author James M. Cain later admitted that if he had come up with some of the solutions to the plot that screenwriters Billy Wilder and Raymond Chandler did, he would have employed them in his original novel.
Edward G. Robinson's initial reluctance to sign on was largely because he had been demoted to third lead. Eventually, he realized that he was at a transitional phase of his career, and was getting paid the same as Barbara Stanwyck and Fred MacMurray for doing less work.
Due to strict wartime food rationing, policemen were stationed in the store where a scene with Fred MacMurray and Barbara Stanwyck was filmed, to make sure nobody on the film crew was tempted to take away any of the food. Paramount released publicity stills showing four policemen in the store with MacMurray and Stanwyck.
The house used as Barbara Stanwyck's character's home still stands today at 6301 Quebec Drive.
When Walter Neff first meets Phyllis Dietrichson, much attention is paid to her ankle bracelet ("anklet"). Urban legend states a married woman wears an anklet on her RIGHT ankle it indicates she is married but available to other men.
Raymond Chandler: man sitting outside Barton Keyes' office reading a magazine who glances up at Walter Neff as he walks past, about 16 minutes into the movie.