It is a well-known fact that after epilepsy surgery (ES) preexisting psychopathology may deteriorate or de novo psychopathological syndromes, mainly of a depressive and psychotic nature, may appear. Previously, recovery of obsessive-compulsive disorder (OCD) after ES has been reported in patients who had comorbid OCD preoperatively; however, there have been no reports on the appearance of de novo OCD interfering with daily living activities post-ES. This is the first report of OCD after ES in patients with mesial temporal lobe epilepsy (MTLE). Five patients with MTLE were identified with obsessive personality traits before surgery. Within the first 2 months after ES, two of these MTLE patients fulfilled OCD diagnostic criteria. These OCD patients were not any different from the other three patients with respect to age, age of onset of epilepsy, seizure types, and seizure frequency. All patients stopped having seizures postoperatively, but the OCD patients had worse quality of life postoperatively than preoperatively. Our findings show that those patients with obsessive traits preoperatively should be carefully monitored after ES. (C) 2003 Elsevier Inc. All rights reserved.