Changes of reduced glutathione (GSH) and TBARS (thiobarbituric acid-reactive products of lipid peroxidation) concentrations and activity of gamma-glutamyltransferase (GGT, EC 2.3.2.2) in the blood of Lohman brown cockerels and pullets in response to 48 hour food deprivation and 24 hour refeeding were examined. The experiment was performed on 61-day-old chickens. Blood samples ware collected from the wing vein (v. brachialis) in heparinized tubes for three times: control sampling before fasting, then after 48 hour food deprivation and after refeeding for 24 hours. Blood GSH concentration after refeeding in cockerels was significantly higher compared with prefasting and fasting values. The concentration of GSH in female chickens was significantly lower after fasting as well as after refeeding compared with control values. In addition to that, in pullets GSH concentration in refeeding was higher than in fasting conditions. The level of TBARS in blood in female and male chickens after fasting and refeeding were significantly lower than the prefasting values. The GGT activity on cockerels after 48 hour food deprivation was significantly higher compared with control sampling and in chickens refeed for 24 hours, whereas in pullets significant difference was exhibit compared only with control values. Concentration of GSH in control sampling in cockerels compared with those in pullets was significantly lower. After 48 hours of fasting, the level of GSH was significantly higher in the cockerels than in the pullets. Results of TBARS concentration in the pullets were higher of control and fasting values than in the cockerels. The GGT activity of control sampling was significantly higher in male chicken. Lipid peroxidation in chickens of both sexes decreased with fasting, but prooxidative-antioxidative processes were more intensive in female chickens, probably because they were not reach sexual maturity.