The aim of this study was to investigate the influences of different stress models on the antioxidant status and lipid peroxidation (LPO) in erythrocytes of rats. Swiss-Albino female rats (3 months old) were used in this study. Rats were randomly divided into the following four groups; control group (C), cold stress group (CS), immobilization stress group (IS) and cold + immobilization stress group (CS + IS). Control group was kept in an animal laboratory (22 +/- 2 degrees C). Rats in CS group were placed in cold room (5 degrees C) for 15min/day for 15 days. Rats in IS group were immobilized for 180 min/day for 15 days. Rats in CS + IS group were exposed to both cold and immobilization stresses for 15 days. At the end of experimental periods, the activities of glucose-6-phosphate dehydrogenase (G-6-PD), Cu,Zn-superoxide dismutase (Cu,Zn-SOD), catalase (CAT) and glutathione peroxidase (GSH-Px), and concentration of reduced glutathione (GSH) were measured. LPO was determined by measuring the contents of thiobarbituric acid-reactive substances (TBARS). Cu,Zn-SOD activity and TBARS concentration were increased after cold and immobilization stresses, but CAT and GSH-Px activities and GSH levels were decreased. Immobilization stress decreased the activity of G-6-PD. The activities of G-6-PD, CAT and GSH-Px, and the level of GSH were lower in CS + IS group than in the control group. Cu,Zn-SOD activity and TBARS levels were increased in CS + IS group when compared with the control group. From these findings, three stress models are thought to cause oxidative stress.