Characteristic E.E.G. patterns in thalamus and hypothalamus were found during stereotaxic animal experiments. Intralaminal nuclei, dorsomedial nucleus and pulvinar in thalamus, and anterior and posterior nuclei in hypothalamus were either stimulated or coagulated with using radiofrequency generator(RF) in this study. The major rhythmic activity of thalamus and hypothalamus the delta to theta frequency was changed following RF stimulation or coagulation of above mentioned areas. According to the increases of stimulation voltage the rhythmic pattern of thalamus and hypothalamus, altered from synchronization to desynchronization activity. The rhythmic activity, however, showed suppression on coagulation of thalamus and hypothalamus. The modulation of cortical E.E.G. was concerned among thalamus, hypothalamus and brain stem. However it was controlled mainly by the brain stem. The alteration of electrical activity of thalamus and hypothalamus was clearly demonstrated on our study during stereotaxic surgery in human being.