The benzodiazepine hypnotics triazolam (T) (0.25, 0.5 and 1.0 mg), nitrazepam (N) (10 mg) and flunitrazepam (F) (2.0 mg) were investigated with respect to night-time effects and day-time residual effects, in healthy, young subjects. Drug or placebo was taken orally at home before bed-time. Tests for residual drug effects were administered in the laboratory throughout the following day. They included multiple sleep latency tests, the digit cancellation test, questionnaires, self-ratings and experimenter ratings. In addition, motor activity was recorded with a wrist-worn activity monitor during the drug-night, the day following drug intake, and the two subsequent nights. Residual effects consisted of reduced day-time motor activity (T 0.5, F 2.0), enhanced self-rated day-time sleepiness (T 1.0, F 2.0), increased experimenter-rated tiredness (T 0.5, F 2.0), and impaired performance in the digit cancellation test (F 2.0). Grogginess was a common symptom in the morning after flunitrazepam. All drugs reduced motor activity during sleep, and increased subjective depth and quietness of sleep. Increased motor activity in the second post-drug night was observed after triazolam 0.5 mg. The results indicate that a small dose of a short-acting benzodiazepine may be appropriate for promoting sleep without subsequent day-time residual sequelae.