Male and female patients (42) were studied with the mescaline-chlorpromazine technique following premedication with either diethazine, promethazine, chlor-promazine or saline. Anxiety and symptom formation were significantly reduced when either chlorpromazine, diethazine or promethazine was used before mescaline. Patients receiving diethazine before mescaline had great difficulty in verbalizing their feelings or thoughts. Five of 13 patients developed a state featured by muscular weakness. staggering gait, difficulty in verbalization and acute panic. Therapeutic results were poor where the phenothiazine compounds were used as premedication.