• We assessed 96 patients with obsessive-compulsive disorder for DSM-III personality disorder diagnoses with a standardized interview instrument (Structured Interview for the DSM-III Personality Disorders). Fifty patients (52%) met criteria for at least one personality disorder, with mixed, dependent, and histrionic personality disorders most frequently diagnosed. Compulsive personality disorder was diagnosed in only 6 patients (6%), 5 of whom had had onset of obsessive-compulsive symptoms before the age of 10 years, indicating that DSM-III compulsive personality disorder is not invariably a premorbid condition for the development of obsessive-compulsive disorder. Schizotypal personality disorder, at 5%, was found to be less common than in past samples, reflecting differences in either assessment methods or sampling.