Due to the effects of psychiatric drugs (tranquilizer, antidepressants and neuroleptics), especially sedation, it is to be expected that they impair performance (attention, concentration, reaction time etc.) that is indispensable for driving safely. This expectation is verified in experimental studies. The duration and intensity of performance depend essentially on the substance, the dosage, the space of time between application and driving' the duration of therapy and the strength of the basic illness. The intensity of impairment is highest at the beginning of the therapy, at this time, the degree of impairment equals the deficits concerned by more than 0.05% alcohol. The impairment decreases with increasing time of treatment. The danger to traffic safety will be minimized by appropriate prescription (substance and dose), useful hints to the patient and optimal behavior of the patient concerning driving in relation to drug intake.