Subjects were examined after a 40% reduction of the customary sleep ration and after 72-hour sleep deprivation with a group of tests consisting of blood pressure, Johnson-Paschal code, addition, Miles pursuit-meter, pursuit pendulum, Miles ataxiameter, Thorndike Intelligence Examination Part I. The effects of the reduction were not pronounced, with apparently complete recovery after 2 or 3 hours of extra sleep. Greater losses are seen in consequence of the 72-hour deprivation. An individual's normal amount of sleep cannot be curtailed or eliminated without loss of efficiency. It is possible that sleep seizures come in cycles similar those of hunger. (PsycINFO Database Record (c) 2012 APA, all rights reserved)