The aim of the study was to investigate the influence of administration of chlorpyrifos and/or enrofloxacin on the activity of chosen antioxidative enzymes i.e.: superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in erythrocytes of rats. Chlorpyrifos was administered by stomach tube during 28 days at a dose of 3 mg/kg bw (0.02 LD50), and enrofloxacin was administered by stomach tube at a dose of 5 mg/kg bw during 3 subsequent days. It was stated that administration of enrofloxacin at applied dose did not cause any major changes in the activity of investigated antioxidative enzymes. The four-week exposure of rats to chlorpyrifos caused noticeable decrease in SOD and CAT activity in erythrocytes of rats at the beginning of the experiment (up to 24th hour) in comparison with the control group. The activity of GPx during all periods of the experiment was increased. In the group of animals in which both chlorpyrifos and enrofloxacin were applied, the profile of changes in activity of examined enzymes was similar to that one, which was observed after administration of chlorpyrifos exclusively, what may indicate lack of co-action between compounds used in the experiment.