For the purpose of studying the functional condition of the CNS the authors recorded the electrical activity of the brain (by the method of electroencephalography) in parallel with determination of the adrenal cortex function in patients with Itsenko-Cushing disease to whom diphenin was prescribed. Results of investigations showed reduction of the adrenal cortex function in patients with Itsenko-Cushing disease under the effect of diphenin to occur in parallel with reduction of irritation in the brain structures, detected by EEG. The data obtained confirmed an important role played by disturbances of the nervous regulation mechanisms in the appearance of this pathology.