The influence of the L-DOPA preparation on the bioelectrical activity of the brain was studied in 15 patients with Itsenko-Cushing's disease and in 12 patients with diencephalic obesity. L-DOPA administration caused an increase of the theta-rhythm index in the anterior leads in comparison with the initial recording, although the periods of detection of this elevation differed in various patients. No changes of the character of the EEG recording during the test with L-DOPA in comparison with the background recording was revealed in the patients with Itsenko-Cushings disease.