Fifty patients who experienced partial seizures were imaged with computed tomography (CT) and magnetic resonance imaging (MR); 14 of these also had imaging studies of local cerebral glucose metabolism with positron emission tomography (PET). Thirteen patients with attenuation abnormalities on CT scans also had abnormal signals on MR images; ten other patients had MR-image signal abnormalities but normal CT scans. In all seven patients undergoing PET who had MR-signal and sometimes also CT-attenuation abnormalities, areas of metabolic asymmetry were present. Positive PET scans were also seen in three patients with no evidence of abnormality on CT and MR studies. Focal cerebral substance loss on CT and MR studies, present in 21 patients, did not correlate well with electroencephalographic findings. MR is utilized as the initial imaging procedure in patients with partial seizures because it is more readily available and less invasive than PET and more sensitive than CT scanning.