Suriclone is a new anxiolytic drug belonging to the family of cyclopyrrolones. The effects of acute and repeated doses of suriclone on subjective sleep, psychomotor performance and cognitive function were compared to those of placebo in young and elderly volunteers. Young volunteers randomly received suriclone 0.2 mg, 0.3 mg, 0.4 mg or placebo tid, and the elderly received suriclone 0.1 mg, 0.2 mg or placebo tid. After the first single dose and after a three-day treatment, subjects completed at 1, 2, 4, 12 and 24 h after drug administration the following battery of psychomotor and cognitive tests: critical flicker fusion threshold, choice reaction time, simulated car tracking test, the stroop test and the Sternberg memory scanning task. Visual analogue scales and the Leeds sleep evaluation questionnaire were also administered during the study. No significant effects of suriclone compared to placebo were seen on the psychomotor tests both in young and elderly volunteers. The only significant result was an improvement of the ease of getting to sleep in the young with 0.4 mg suriclone tid. In conclusion, there is little evidence to suggest that suriclone produces any measurable behavioural toxicity, so often seen with many of the benzodiazepines, in either young or elderly subjects.