Biochemical parameters of the plasma were studied in mice at different stages of the development of depression-like states in males after social defeats in 10 and 20 intermale confrontations (T10 and T20 victims, respectively). Glucose and cholesterol levels were increased in T10 victims in comparison with intact animals. In T20 victims the increase in glucose level was paralleled by an increase in total protein. T20 victims differed from T10 victims by lower catalase activity.