Data from evening questionnaires, reports of side effects, laboratory findings, and all-night respiratory measurements were collected on the 99 chronic insomniacs examined in this multicenter study. These data were used to compare the clinical safety and desirability of a benzodiazepine hypnotic with a very short half-life, midazolam 15 mg, with a hypnotic with a longer half-life, flurazepam 15 and 30 mg; both compounds were compared with a placebo control. There were 2 prestudy placebo nights followed by 14 consecutive nights of treatment. Of the 107 patients accepted, 99 completed the study. No marked adverse reactions were found in any area for any group. There was no increase in sleep apneas during the treatment period for any group. Results of this study provide additional evidence of the safety of benzodiazepine hypnotics.