The yield of magnetic resonance (MR) imaging was investigated in 30 patients with partial complex epilepsy, and the results were compared with those of computed tomography (CT). Magnetic resonance imaging and CT disclosed focal cerebral abnormalities in 13 (43%) and eight (26%) patients, respectively. Two additional focal temporal lesions were identified by double-dose CT scanning, increasing the yield of CT to 33%. Magnetic resonance images were abnormal in all patients with focally abnormal CT scans, and in four patients (50%) they defined the extent of the temporolimbic lesions better than did the CT scans. Two of these patients had gliomas. In addition, MR images were focally abnormal in 85% of the patients in whom scalp electroencephalograms showed focal ictal discharges. These data indicate that MR imaging is more informative than CT in partial complex epilepsy.