The aim of the study was to estimate beneficial effects of L-arginine, a nitric oxide precursor, on antioxidant enzymes activity (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, ceruloplasmine), the lipid peroxidation processes level and parameters of membrane erythrocytes resistance before and after lead intoxication in rats with different resistance to hypoxia. Our results suggest that the antioxidant system enzymes activity and lipid peroxidation processes level in animals which differ in sensitiveness to hypoxia, are higher in animals with low resistance to hypoxia in the control group. We have shown that the amino acid, L-arginine, is an efficient antioxidant capable of reducing the level of lipid peroxidation processes in blood of lead-preexposed rats. L-arginine treatment under lead intoxication caused alteration in antioxidant enzymes activity due to increasing the enzymes activity of glutathione system, especially in animals with low resistance to hypoxia. The influence of L-arginine under lead intoxication was investigated to ascertain whether this amino acid possesses antioxidant properties before lead injection (preventive effect) and whether L-arginine has therapeutic effects by treatment after lead intoxication. We have shown a significant protective effect of L-arginine under treatment with a preventive effect before lead intoxication. These studies suggest that L-arginine may be a useful drug in treatment under lead intoxication.