Three patients with multiple personality disorder and three with obsessive-compulsive disorder were compared on a variety of self-report measures and on two structured interviews. Amytal Sodium interviews had been conducted on the obsessive patients; alter personality-like entities claiming responsibility for the obsessions and compulsions were contacted in two patients. The one obsessive patient with no alter personality differed markedly from the other five on the SCL-90, the Lynfield Inventory, and the Dissociative Experiences Scale. Structured interviews with the Anxiety Disorders Interview Schedule and the Dissociative Disorders Interview Schedule also clearly differentiated this patient from the other five. It appears that there is a phenomenological overlap between multiple personality disorder and some cases of obsessive-compulsive disorder. Obsessive patients with prominent dissociative features may be a psychologically and biologically distinct subgroup.