Two psychiatrists, using standardized clinical examinations, found that 21% of 125 patients newly admitted to nursing homes had delusions. The psychiatric disorders associated with these delusions are described. Delusional patients were more behaviorally disturbed before admission than nondelusional patients. These behavior problems were often the reason for admission, and they persisted after admission. Nursing home staff members infrequently identified and often inappropriately treated delusional patients. Since delusions are an important potentially treatable cause of behavior problems in nursing home residents, the authors suggest ways to improve the recognition and management of delusions.