Abstract: The short- and intermediate-term actions, as well as the carryover and withdrawal effects, of quazepam, a new benzodiazepine hypnotic with a half-life of 60 to 100 hours, were compared with those of triazolam, a triazolodiazepine hypnotic with a half-life of 2 to 3 hours. Both the subjective effects of these drugs as well as their objective actions on the sleep EEG were sought. The study was conducted on two groups of six subjects with chronic insomnia who ranged in age from 32 to 56 years. Each subject was studied for 25 consecutive nights. Placebo was administered at bedtime on the first four nights, followed by 30 mg quazepam or 0.5 mg triazolam on the next 14 nights and by placebo again on the ensuing seven withdrawal nights. Both drugs increased the total sleep time during their administration and improved the subjective quality of sleep. Major differences, however, were observed on withdrawal. A significant and marked decrease in the total sleep time occurred with triazolam on the first withdrawal night. With quazepam, rebound insomnia was not observed at any time during the seven-day withdrawal period.