The cognitive function and psychomotor performance of 10 healthy male volunteers were measured following single oral doses of: zopiclone (7.5 mg), flurazepam (15 mg), lormetazepam (1 mg), triazolam (0.25 mg) and placebo. The performance tests selected (stroop task, five choice serial reaction time, memory span, logical reasoning, mood and saccadic eye movement analysis) were thought to reflect aspects of normal daily activity. The tests demonstrated a clear reduction of performance for all active treatments. No drug emerged as the most potent sedative overall, as each of the tests was affected to a different degree by each drug. Drug effects were not qualitatively different between active treatments so that zopiclone was indistinguishable from the three benzodiazepines with which it was compared.