The amt. of insulin necessary to produce shock may vary from 25-400 units, the tolerance varying with each individual and even in the same individual during treatment. Each patient usually reacts to a "shock" dose of insulin along a definite pattern[long dash]perspiration, bradycardia, hypothermia, motor restlessness, coma and occasionally convulsions. Biochemical studies of 32 blood constituents were made before, during, and after treatment. Sugar and fermentable sugar remained at a low level throughout the individual treatment and there was a simultaneous reduction in inorganic P. Brain action potentials were studied in 17 of the schizophrenic patients treated. Two distinct types of brain waves were noted in 50 records. In 42, a fairly normal [alpha] rhythm, 8-10 cycles per sec, predominated during the early interval of recording and as the hypoglycemia progressed the frequency decreased, a frequency brain wave pattern of 3 cycles per sec. predominating. These slow waves were independent of whether the eyelids were open or closed. In 8 records the frequency of the brain wave pattern fluctuated irregularly between a 4 to 5 and 10 cycles per sec. rhythm. There was a striking parallelism between the variations in brain potentials and the changes in blood sugar content, and with intraven. glucose the return of the brain wave pattern to the original preinsulin type was rapid. Of 140 schizophrenic patients treated, 35 were in remission, 25 improved, 79 showed no change.