Sixteen patients with drug-resistant complex partial epilepsy were, during preoperative investigations for surgical treatment, subjected to intravenous methohexital and amobarbital EEG activation tests. The interictal epileptic spike discharges were visually counted on the seizure-generating side and compared with those found in the contralateral hemisphere. The invasive recordings were made with depth electrodes implanted in the mesial temporal lobes of 5 patients, and with subdural strip electrodes in varying lateral positions over the frontotemporal-parietal lobes of the other 11 patients. The doses of 10% amobarbital, 50-200 mg, were too low to induce any significant activation. In eight patients with unilateral epileptic lesions, 10, 25 and 50 mg 1% methohexital, induced a dose-dependent increase in the interictal spiking, always higher on the side of the seizure-gererating focus. Asymmetric induction of beta activity was noted in five patients. The test gave valuable information when determining the type or location of the epileptic abnormality. Parallels were drawn with earlier studies on spike-activation tests after intracarotid amobarbital injections. Although administered differently, the barbiturates are supposed to act directly on the neurons, and not via integrative wakening mechanisms.