Seventeen obsessive-compulsive disorder patients treated with psychosurgery were administered a comprehensive neuropsychological test battery. Their performance on neuropsychological testing was compared with that of an age and severity matched sample of 17 OCD sufferers who had not received psychosurgery. The psychosurgery and control groups did not differ in intellectual or memory functioning, consistent with earlier findings that psychosurgery does not reduce global ability estimates. The psychosurgery group performed more poorly than the control group on an adaptation of the Wisconsin Card Sorting Test, demonstrating the possible impact of frontal lobe lesions on the abilities underpinning the formation and shifting of response sets.