1 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. 2 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. 3 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. 4 Drug effects were not qualitatively different between active treatments so that zopiclone was indistinguishable from the three benzodiazepines with which it was compared.