In three parallel groups, brief and intermittent administration and withdrawal of triazolam, 0.5 mg, temazepam, 30 mg, and placebo were assessed in a 12-night sleep laboratory study of 18 subjects with insomnia. With this intermittent schedule both drugs improved sleep, with about one-third reduction in total wake time; this reduction was significant for temazepam but not for triazolam. Even though the periods of drug administration were quite brief, withdrawal of triazolam consistently produced rebound insomnia, with increases in total wake time above baseline of 61% and 51%, respectively, for the first night of each withdrawal period. With temazepam this effect was more variable, with total wake time increased only with the second withdrawal period (39%). Thus these findings indicate that even under conditions of brief, intermittent use and withdrawal, triazolam and, to a lesser degree, temazepam produce rebound insomnia after abrupt withdrawal, thereby predisposing to drug-taking behavior and increasing the potential for drug dependence.