1. The physiological and psychological effects of i. v. pervitin, sodium amytal, and benzedrine were studied in 75 psychiatric cases.2. Pervitin has cephalotropic and sympathecotropic effects. It is a more potent cephalotropic and less potent sympathecotropic drug than benzedrine.3. Pervitin produces an emotionally charged free flow of material, which may include painful memories, traumatic experiences, intimate personal phantasies, and delusional ideas. Most patients experience a dramatic relief of tension and feeling of relaxation. Mild depressions are often delayed. The psychologically rich response evoked by pervitin is helpful both diagnostically and therapeutically.4. The physiological effects of pervitin include evaluation of blood pressure for 24-36 hours, alteration of pulse rate, dryness of the mouth with thirst, loss of appetite, tightness in the chest, increased awareness of the environment and of sensory stimuli, elimination of fatigue, and wakefulness.The EKG is not significantly altered. The EEG shows no striking change in basic frequency pattern despite pronounced psychophysiological effects. There is a slight decrease in alpha wave output during the stage of tension and hyperalertness.5. A comparison of pervitin with sodium amytal and benzedrine reveals the following:(a) In contrast to sodium amytal, pervitin evokes a more spontaneous, richer, and more appropriate response. In some cases, when sodium amytal fails to produce a response, pervitin succeeds. With pervitin there is no loss of consciousness or amnesia for the interview. All the material dealt with during the pervitin interview may be recalled, and is available to the patient's consciousness for integration and assimilation.(b) Benzedrine in doses of 20 to 40 mg. produces similar physiological effects as pervitin, but fails to produce the same intense psychological response. The productions with benzedrine lack the depth and personal significance of those with pervitin.(c) Pervitin may counteract the hypnotic effect of amytal, and amytal may calm the overexcitement occasionally induced by pervitin.