Background/Aim. It is weel-known that sulphur baths and mud paks demonstrate beneficial effects on patients suffering from degenerative knee and hip osteoarthritis (OA) through the increased activity of protective antioxidant enzymes. The aim of this study was to assess lipid peroxidation level, i.e. malondialdehyde concetration, in individuals with knee and/or hip osteoarthritis (OA), as well as to determine the influence of sulphur baths and mud packs application on the activity of superoxide dismutase (SOD) and catalase (CAT) in order to minimize or eliminate excessive free radical species production (oxidative stress). Methods. Thirty one patiens with knee and/or hip OA of both sexes were included in the study. All OA patients received mud pack and sulphur bath for 20 minutes a day, for 6 consecutive days a week, over 3 weeks. Blood lipid peroxidation, ie malondialdehyde concentration, superoxide dismutase and catalase activity were measured spectrophotometrically, before, on day 5 during the treatment and at the end of spa cure. Healthy volunteers (n = 31) were the controls. Results. The sulphur baths and mud packs treatment of OA patients caused a significant decrease in plasma malondialdehyde concentration compared to the controls (p < 0.001). The mean SOD activity before the terapy was 1 836.24 U/gHb, on day 5 it rose to 1 942.15 U/gHb and after the spa cure dropped to 1 745.98 U/gHb. Catalase activity before the therapy was 20.56 kU/gHb and at the end of the terapy decreased to 16.16 kU/gHb. The difference in catalase activity before and after the therapy was significant (p < 0.001), and also significant as compared to control (p < 0.001). At the end of the treatment significant increase of hemoglobin level and significant decrease of pain intensity were noticed. Conclusion. A combined 3-week treatment by sulphur bath and mud packs led to a significant decrease of lipid peroxidation in plasma, as well as pain intensity in the patients with OA. These changes were associated with changes in plasma activity of SOD and CAT and a significant increase of hemoglobin level suggesting their role in beneficial effect of spa therapy in the patients with OA.