Obsessive compulsive disorder shares numerous clinical features with other anxiety disorders. To study the relationship between OCD and other anxiety disorders, the authors administered the Structured Clinical Interview for DSM-III to 36 OCD patients. Thirty-nine percent (14) of patients reported a lifetime history of panic attacks, and 14% (5) met DSM-III-R criteria for panic disorder at the time of interview. Fourteen percent (5) met criteria for social phobias, and 19% (7) met criteria for simple phobias. Eighteen patients were treated with clomipramine in doses of at least 100 mg/day for 3 months. Patients with a history of other anxiety disorders responded significantly better to clomipramine.