While outpatients or other users of therapeutic drugs have to be informed about the risk of impaired functioning during driving or work, the prescribing physician needs to be familiar with the side effects of alternative drugs in order to select the most suitable treatment. With this aim, several types of benzodiazepine anxiolytics in low anxiolytic doses (diazepam 5 mg or 10 mg, nitrazepam 5 mg, oxazepam 10 mg, medazepam 10 mg, and alprazolam 0.2 or 0.5 mg-per 2m2 body surface) were tested under laboratory conditions for their effects on vigilance performance. In a double-blind design, 145 healthy volunteers performed a 60 min vigilance test (composed of discriminatory reactions to acoustic stimuli and a secondary visual tracking task) and four short psychomotor tests (lasting 1-7 min each) before and after a single dose of drug or placebo. Subjects described their perception of the drug effect with the help of a mood check list, and fatigue, sleepiness, and effort scales. Only diazepam 5 mg and 10 mg, alprazolam 0.5 mg, and nitrazepam 5 mg caused significant deterioration in vigilance performance along with perceived sleepiness and the need for a greater effort to overcome it. The onset of diazepam effect was quicker, whereas alprazolam effect lasted longer. No effect was noted in the short psychomotor tests except for the Bourdon Cancellation Test, where the first phase of diazepam effect was registered.