If the differential specific anxiolytic activity between various benzodiazepines remains controverted , the clinician nevertheless now possesses scientific data allowing him to make a more rational selection, in order to obtain a better overall efficacy, either for an anxiolytic or hypnotic action. In other respects, the concept of anxiety has evolved and given rise to distinctions that will need to be taken into account in the choice of the adequate psychotropic medication, either a benzodiazepine or another psychotropic drug. When a benzodiazepine must be prescribed, the main criteria involved in its choice need to be considered. As anxiolytic medication, besides a selective action on anxiety, the absence of cumbersome effect on psychomotor activity and vigilance, pharmacokinetics constitute an important factor that must be looked at. Although the classification of benzodiazepines according to their half-life is only an approximation, some overlapping being possible between the various groups, it proves nevertheless extremely useful with respect to the therapeutic goal considered and the various clinical parameters involved. Some other aspects must also be considered, for example the rebound phenomenon. Finally, the variability of individual responses to drug treatment must be remembered.