In this paper a study about traffic accidents by means of psychodiagnostic battery is presented, which consists of tests for measuring real states (experience of psychic loading and labor satisfaction), and premises of relatively stable performance (concentration for attention). Two groups of drivers from an urban bus depot were studied: those involved in accidents and those not involved. No differences were found between both groups concerning concentration, but it was for the other aspects. In this study a statistical methodology was used that can be employed in similar studies for the comparison of groups.