The purpose of this study was to compare psychosocial functioning in patients with schizotypal, borderline, avoidant, or obsessive-compulsive personality disorder and patients with major depressive disorder and no personality disorder. Patients (N=668) were recruited by the four clinical sites of the Collaborative Longitudinal Personality Disorders Study. The carefully diagnosed study groups were compared on an array of domains of psychosocial functioning, as measured by the Longitudinal Interval Follow-Up Evaluation--Baseline Version and the Social Adjustment Scale. Patients with schizotypal personality disorder and borderline personality disorder were found to have significantly more impairment at work, in social relationships, and at leisure than patients with obsessive-compulsive personality disorder or major depressive disorder; patients with avoidant personality disorder were intermediate. These differences were found across assessment modalities and remained significant after covarying for demographic differences and comorbid axis I psychopathology. Personality disorders are a significant source of psychiatric morbidity, accounting for more impairment in functioning than major depressive disorder alone.