As part of a systematic investigation of the possible brain sites at which benzodiazepines (BZ's) alter sleep, 0.5 Mu g of triazolam was injected into the dorsal raphe nucleus (DRN) of rats. Injections of triazolam to the DRN significantly increased sleep latency and decreased nonREM sleep as compared to injections of vehicle to the DRN or injections of triazolam to brain areas near but outside the DRN.