['Depression sometimes occurs after surgical treatment for medically intractable partial epilepsy. The risk of pre- and postsurgical depression may vary by laterality of seizure focus. We reviewed the pre- and postsurgical psychological assessments and clinical courses of patients to identify those at highest risk for postsurgical mood disorders.', 'Depression status was assessed in a consecutive series of epilepsy patients before and 1 year after epilepsy surgery with the use of Scale 2 of the MMPI-2 and a clinical depression index (CDI) scoring the occurrence of depressive symptoms, psychiatric referral, or attempted/completed suicide. Outcome at 1 year was modeled by regression techniques as functions of preoperative mood measurements, side of epilepsy surgery, and preoperative verbal intelligence.', 'The CDI and Scale 2 MMPI-2 correlated significantly (r = 0.341; p < or = 0.01). Left (n = 54 subjects) and right (n = 53) surgery groups did not differ by sex, seizure outcome, age, education, age at first seizure, duration of epilepsy, or intellect. Higher presurgical depressive morbidity (p = 0.0037) and right-sided surgery (p = 0.0003) predicted higher postoperative CDI. Higher preoperative Scale 2 scores, indicating worse depressive traits, predicted worse postoperative Scale 2 scores (p < 0.0001). Although side of surgery did not predict Scale 2 scores, Scale 2 scores of patients with preoperative right-sided foci tended to have worse postsurgical Scale 2 scores (p = 0.08). Findings for the temporal lobectomy subgroup (n = 90) were similar to those of the overall sample.'] Does depression in intractable partial epilepsy vary by laterality of focus and surgery?