In 52 studies, performance data were obtained the next day following bedtime ingestion of a sedative-hypnotic or a placebo. Only eight of these studies used insomniac patients. Most studies used young adult males. Benzodiazepine hypnotics were most frequently administered and psychomotor performance was most often measured. Little consistent data are available on cognitive functioning and more complex behavior. Drug-related improvement in performance was not found, and, in comparing active drug to placebo, it is clear that all hypnotics, at some doses, produce decrements in performance the next day. Higher doses consistently showed a decrement, and this decrement was usually persistent over the entire day. Although long-acting drugs generally showed more performance decrement, half-life data were not consistent.