Mescaline, cocaine, sodium amytal and benzedrine were given to 14 schizophrenic patients, and their influence upon personality functions and the electroencephalogram (EEG) was observed. Changes in the EEG were found only when definite psychological changes took place. The effects of the drugs could be classified into two types: 1) Those specific for a given drug. Psychologically these were manifested in changes in attitude, anxiety, mood, etc. Correlated with the most extreme states of anxiety produced by mescaline was a 25 to 30 per cent increase in frequency of the 10-per-second (alpha) rhythm. With sodium amytal the decreased tension was accompanied by the appearance of a 15 to 20-persecond (beta) rhythm. 2) Those characteristic of a given patient. Psychologically these took the form of elaborations within the content of the psychosis and the patient's reaction to the setting, regardless of which drug was used. Similarly, a change in per cent time alpha of the EEG was consistent in a given patient either in the direction of increase or decrease.