The short-term hypnotic efficacy of 15 mg flurazepam was evaluated in nine patients (mean age 37.2 +/- 15.9 years) who complained of insomnia and had polysomnographic evidence of disturbed sleep. Patients slept in the laboratory 14 consecutive nights, and their sleep was monitored using standard polysomnographic procedures. Prior to bedtime, they received a placebo the first four nights, 15 mg flurazepam on nights 5 through 11, and a placebo again on nights 12 through 14. Flurazepam significantly increased total sleep time while reducing the latency to stage 1 sleep, the number of awakenings in the night, and the amount of wakefulness after sleep onset. Sleep stage patterns also were altered significantly with flurazepam: percentage stage 2 sleep increased, and percentages of 3-4 sleep and REM sleep (on drug night 1 and nights 1-3) decreased. With the exception of REM sleep, most of these drug effects were first detected on the second night of administration, did not diminish over the next six nights, and persisted during the three-day withdrawal period. Subjective evaluations of sleep generally corresponded with the polysomnographic data. It was concluded that 15 mg flurazepam has significant hypnotic properties with minimal adverse side effects.