Repeated doses of triazolam 0.5 mg and mitrazepam 10 mg were given to two groups of consenting volunteers. 2. Measures of choice reaction time, critical flicker fusion threshold, and mental arithmetic ability were made the morning following nocturnal medication with either the active drug or placebo. 3. The subjects' assessment of sleep and early morning behaviour were obtained on 10 cm-line visual analogue scales. 4. Both drugs were rated as effective hypnotics while, at the same time, ratings of the ease of awakening from sleep and the errors produced in a mental arithmetic task were impaired. 5. Objective measures of performance and subjective reports of "hangover" differentiated nitrazepam from triazolam. A significant impairment of early morning performance found with nitrazepam was not found following treatment with triazolam.
