The records of electrical stimulation of 30 psychomotor epileptics were examined for threshold levels of evoked responses and after-discharge production. Comparisons were made between anatomical sites, operated and nonoperated structures, and different disease states. It was found that patients with hippocampal sclerosis (HS) had higher thresholds in structures on the operated side. The patients with lesions other than HS were found to differ from those with hippocampal sclerosis in that there were no differences found between their diseased and nondiseased structures. For both patient groups, the amygdala had a much higher threshold for after-discharge production than either the hippocampus or the hippocampal gyrus.