A man with onset of obsessive-compulsive disorder (OCD) at age 62 had a large right posterior frontal infarct and occlusion of the ipsilateral internal carotid artery. We review additional cases from the literature with obsessive or compulsive behaviors and structural lesions. OCD may have a structural correlate, and this should be searched for in instances where onset occurs after age 60, is atypical, or is associated with other neurologic signs or symptoms. Rational therapy for OCD will depend on a detailed understanding of the neuronal circuitry and physiologic mechanisms underlying such behaviors, and additional data from thoroughly evaluated patients may be revealing.