<P> Prior to commencement of filming a week of rehearsals started on 4 January 1975 in Oregon, during which the actors watched the patients in their daily routine and at group therapy . Jack Nicholson and Louise Fletcher also witnessed electroconvulsive therapy on a patient . </P> <P> Other than Nicholson, the rest of the cast were working for scale, or a little above that . Fletcher worked for 11 weeks and made $10,000 before taxes . </P> <P> Filming began in January 1975 and concluded approximately three months later, and was shot on location in Salem, Oregon and the surrounding area, as well as on the Oregon coast . </P> <P> The producers decided to shoot the film in the Oregon State Hospital, an actual mental hospital, as this was also the setting of the novel . The hospital's director, Dean Brooks, was supportive of the filming and eventually ended up playing the character of Dr. John Spivey in the film . Brooks identified a patient for each of the actors to shadow, and some of the cast even slept on the wards at night . He also wanted to incorporate his patients into the crew, to which the producers agreed . Douglas recalls that it wasn't until later that he found out that many of them were criminally insane . </P>

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