Data from ten patients with complex partial seizures who underwent positron emission tomography using the 15-0 inhalation technique are presented. Decreased flow and metabolism are noted in the hemisphere ipsilateral to the EEG focus, but, in patients with unilateral foci, bilateral changes in temporal cortex are detected. Other areas maximally affected include the basal ganglia, and the cerebellum. The possible role of anticonvulsant drugs in these findings is discussed.