Patients with obsessive-compulsive disorder (OCD) had lower right-ear advantages than healthy controls on five different language-related dichotic listening tests of cerebral laterality. This abnormality was more pronounced in patients with more severe illness. Stimulus pairs in one test consisted of one word with a positive emotional valence and one emotionally neutral word. Pairs in another test consisted of one negative and one neutral word. Patients with OCD tended to hear fewer emotion-related words than did healthy controls, a finding also noted in depressed patients. Moreover, OCD patients who responded to treatment with serotonin reuptake inhibitors heard fewer emotion-related words than did nonresponders.