The effects of lorazepam (0.25 mg) twice a day on several cognitive and performance tasks, pictures test, digit-symbol substitution test (DSST), choice reaction time (CRT) and critical flicker fusion (CFF), were investigated in healthy students. A double-blind independent group design was used to compare placebo and lorazepam (30 volunteers in each group). After randomisation, all subjects received placebo for 3 days (D), followed by 14 days of treatment, with either lorazepam or placebo. Subjects completed a battery of tests at Do, then D(3), D(7) , D(10) and D(14). D(3) performance was poorer in the lorazepam group except for CFF (ascending values and total values), yet the only significant improvement was in total reaction time on the CRT test. However, a significant improvement of performance was shown at D(7), D(10) and D(14) in the lorazepam group compared with the control group (except in recognition reaction time). The current study shows that low repeated doses of lorazepam are able to produce small improvements in some aspects of psychomotor and cognitive functions in healthy volunteers. Different points are discussed to explain the performance improvement: training effect, tolerance effect, partial inverse agonist effect and the possible release of cholecystokinin.