Interictal positron computed tomography (PCT) with 18F-fluorodeoxyglucose was performed on 50 patients with partial seizure disorders. Electroencephalographic (EEG) monitoring was carried out during the metabolic studies using scalp and sphenoidal electrodes in 33 patients and stereotaxically implanted depth electrodes in 17. Four patients in this series had focal abnormalities on x-ray computed tomographic scans, but these were at the site of the presumed epileptogenic lesion in only 2. One or more discrete zones of hypometabolism were identified in 35 patients, and only 1 patient appeared to show focal interictal hypermetabolism. No quantitative relationship could be demonstrated between the degree of focal hypometabolism and either the frequency of intericatal EEG spikes or the presence of focal nonepileptifor EEg changes. It was concluded that metabolic and electrophysiological techniques measure different aspects of cerebral dysfunction in seizures diorders. Although interictal PCT in patients with partial epilepsy usually demonstrates zones of hypometabolism, this finding, perŕse, does not reveal the epileptic nature of the abnormality.