The cardiovascular effects of benzodiazepines administered intravenously as preoperative sedatives have received considerable study, but sleep laboratory research on benzodiazepines administered orally as hypnotics has not focused on assessment of cardiovascular changes. Analysis of heart rate (HR) data collected in sleep laboratory studies on the effects of 0.5 mg of triazolam (Halcion) and 30 mg of flurazepam (Dalmane) demonstrated that both benzodiazepine hypnotics produced a significant HR elevation that was present for up to 4 h during sleep. By the 3rd night of bedtime administration of triazolam, the HR increase was no longer statistically significant, but on the 5th night of flurazepam administration, HR was still significantly elevated over baseline levels. The HR elevation does not appear to be of clinical significance for most patients. However, this finding indicates that benzodiazepines administered at hypnotic-dose levels have peripheral as well as central effects.