Hemodialyzed patients with chronic kidney disease are prone to atherosclerosis, which occurs due mainly to lipid abnormalities. Abnormal lipid metabolism could result, among others, from increased formation of free radicals and, consequently, oxidative stress in these patients. The objective of the present study was to evaluate the influence of therapy with lovastatin or with a hypolipemic diet only on oxidative stress in hemodialyzed patients. We addressed the issue by measuring the total antioxidant status (TAS) and the level of 8-hydroxy-2-deoxyguanosine (8-OHdG), an oxidative DNA damage metabolite, in the serum. The study group consisted of 71 patients. They were divided into 3 groups: treated with lovastatin (20 mg/day, n=30), with a hypolipemic diet alone (n=28), and untreated controls (n=13). Serum levels of TAS and 8-OHdG (8-hydroxy-2-deoxyguanosine) were determined. Blood samples were collected at the beginning of the study and then after a 6 months' therapy. We found that the level of 8-OHdG decreased considerably only in the lovastatin-treated group; the decrease was from 15.6+/-8.1 to 12.5+/-4.8 ng/ml (P=0.04). In the other two groups changes in 8-OHdG were insignificant. The level of TAS increased significantly in the lovastatin-treated group from 1.28+/-0.20 to 1.37+/-0.116 mmol/l (P=0.011), decreased in the diet-treated group from 1.55+/-0.14 to 1.45+/-0.11 mmol/l (P=0.007), and remained unchanged in the untreated group (1.42+/-0.11 vs. 1.40+/-0.12 mmol/l). We conclude that lovastatin, but not a hypolipemic diet alone, exerts an antioxidant effect in hemodialyzed patients. However, the determinants of the antioxidant effect of statins in patients with chronic renal failure are unclear and their resolution would require alternative study designs.