Objective: The aim was to establish the prevalence of eating disorders in psychiatric patients. Method: The total inpatient (n = 8,942) and outpatient (n = 10,125) Norwegian psychiatric population was investigated with a staff-report questionnaire. Results: The prevalence of eating disorders in the inpatient population was 3.8% for women and 1.6% for men. In the outpatient population, the differentiated diagnoses anorexia nervosa (AN), bulimia nervosa (BN), and the comorbidity of AN + BN was 5.7%, 7.3%, and 1.6% for women, and 0.8%, 0.7%, and 0.3% for men (this could be reduced to AN and BN prevalences of 7.3% and 8.9% for women and 1.0% and 1.0% for men). Discussion: The level of the prevalence figures is in the expected area, thus the present study confirms earlier studies with smaller psychiatric populations. © 1995 by John Wiley & Sons, Inc.