In order to clarify whether erythrocyte superoxide dismutase (SOD) activity and glutathione system including reduced glutathione (GSH), glutathione peroxidase (G-Px), glutathione reductase (G-Red), glutathione S-transferase (GST) are impaired in men with Behchet's disease (BD) at the first diagnosed time, erythrocyte SOD activity, GSH level, activities of G-Px, G-Red and GST were determined in men with new diagnosed BD. Erythrocyte GSH level, G-Px and G-Red activities were found to be lower, SOD activity was found to be higher in the patients as compared the controls. There was no significant difference between patients and controls for GST activity. Significant positive correlations between GSH and G-Px, GSH and G-Red; significant negative correlations between GSH and SOD, G-Px and SOD, G-Red and SOD were determined. It was concluded that erythrocyte SOD activity and glutathione system are altered in men with new diagnosed BD. It was concluded that these alterations may be a contributory factor for tissue damage associated with BD. © 2002 Tohoku University Medical Press.