The increasing number of traffic accidents connected with rapid development of motorization makes us think of their causes. Regulations by law binding in Poland demand traffic users to be checked up on the presence of agents similar ethyl alcohol. Commonly abused medicines, especially sedative and psychotropic but also hypnotic and analgesic are a great traffic problem. Up to the present analytical procedures and a model medico-legal opinion on the influence of medicines on psychophysical efficiency have not been standardised. In the paper the authors have presented the results of their research on agents negatively influencing the human psychophysical efficiency carried out in the Forensic Medicine Department, Silesian University of Medicine, Katowice. The research comprised individuals involved in both traffic crashes and accidents who (as checked) either where not under the influence of ethyl alcohol or the concentration of ethanol was low (1 per thousand). Positive cases most often showed only one sort of medicines (barbiturates, benzodiazepines or opiates). In other cases barbiturates and benzodiazepines, benzodiazepines and opiates as well as derivatives of benzodiazepine and tricyclic antidepressants were determined. Blood concentrations of all these substances were in a wide range of therapeutic doses.