Sir Alfred Hitchcock was disappointed with the limits of Gregory Peck's facial expressions. According to Peck, "I couldn't produce the facial expressions that Hitch wanted turned on. I didn't have that facility. He already had a preconception of what the expression ought to be on your face, he planned that as carefully as the camera angles. Hitchcock was an outside fellow, and I had the Stanislavski training from the Neighborhood Playhouse, which means you work from the inside."
Sir Alfred Hitchcock was a big admirer of Salvador Dalí's work, and realized that no one understood dream imagery better. Producer David O. Selznick was opposed to using Dalí from an expense point of view, until he realized the marketing mileage that could be gained from such a hiring.
The snow falling on John Ballantyne and Dr. Petersen during the skiing scene was actually cornflakes.
Sir Alfred Hitchcock referred to this movie as "just another manhunt wrapped up in pseudo-psychoanalysis."
One of the first films to approach the theme of psychoanalysis. However, during production, the director Sir Alfred Hitchcock wanted a long and gripping scene, inviting surrealist artist Salvador Dalí - who had been the cover of Time magazine in December 4, 1936 - to design a grandiose dream sequence. Producer David O. Selznick wanted it to be based on his personal experiences, and brought his psychotherapist in on the set to be a technical advisor. When she disputed with the director on the workings of therapy, Hitchcock responded, "My dear, it's only a movie." After the producer saw the rushes on September 27, 1944, he asked William Cameron Menzies to re-shoot the dream sequence, and drastically reduce it. Hitchcock and Dalí were not on the set for it.
Alfred Hitchcock: (at 37:17) Coming out of the elevator at the Empire Hotel carrying a violin case and smoking a cigarette.