Background. Blood platelets play an important role in many physiological and pathological processes. Their dysfunction may lead to serious illness or death. Numerous exogenic factors may have an adverse impact on platelet metabolic processes by affecting enzymatic reactions. The aim of our study was to determine how catalase (CAT) and superoxide dismutase (SOD-1) are modified by the exogenic electromagnetic field (EMF) occurring in a motor vehicle.Material and methods. Suspensions of human blood platelets were used for this investigation. The suspensions were exposed to EMF with the appropriate characteristics in a specially prepared test stand. Catalase (CAT) and superoxide dismutase (SOD-1) activity were measured in the experimental suspensions and in a control group 30, 60 and 90 min after exposure. Results. A significant increase in catalase activity was observed 30 and 60 min after the exposure. The level of the investigated enzymes decreased 90 min after the exposure, as compared to the control group. A significant decrease in SOD-1 activity was observed at each time point in which the suspension was exposed to EMF, as compared to the control group.Conclusion. The registered changes in catalase oxidative activity point up the active role of this enzyme in platelet defense against the effects of the electromagnetic fields emitted by automobile electronics. The decreased platelet antioxidative efficiency noted during the experiment may be connected with SOD-1 activity reduction.