It has been postulated that ionizing radiation generates reactive oxygen species (ROS). ROS are annihilated by an intracellular enzymatic system composed mainly of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx). Workers of X-ray departments are occupationally exposed to long-term low levels of ionizing radiation, which may affect their antioxidant status. Erythrocyte activities of SOD, CAT and GPx were measured in 45 workers of X-ray departments and 30 persons who constituted the control group. Subgroups with respect to sex and cigarette smoking were selected. Colorimetric method was used for determination erythrocyte activities of SOD, CAT and GPx. A signifi cant decrease of GPx, SOD and CAT activity in workers as compared to controls was observed. Lower activity of SOD and GPx in female and GPx in male subgroup was found. SOD was signifi cantly more elevated in smoking workers than in the non-smoking staff. Moreover non-smoking employees showed lower SOD and GPx activity in comparison to the non-smoking control. GPx decrease was found in smoking workers in comparison to the smoking control. Additionally, smoking workers showed lower activity of GPx and CAT compared to non-smoking control.