The effects of three oral doses of bedtime triazolam (0.25 mg, 0.5 mg, and 1.0 mg) a new benzodiazepine, on the laboratory sleep of insomniacs were studied in a double blind design which used the following 14 consecutive night schedule: 1-4 placebo; 5-11 drug; 12-14 placebo. Effects on sleep were measured objectively by conventional EEG/EOG/EMG sleep recordings and subjectively by questionnaires administered each morning. Side or toxic effects were assessed by screening physicals and questionnaires administered each morning and each evening and by a comparison of the prestudy vs. end-study physical exams and clinical lab tests. At the 0.5 mg dose triazolam significantly reduced several objective and subjective measures of insomnia. It had lesser effects at the 0.25 mg dose and equal or greater effects at 1.0 mg dose. There were no remarkable side or toxic effects at any dose.