Galactosamine model of toxic hepatitis in rats which, as to its morphobiochemical picture, is considered adequate to human hepatitis was used to study the role of disturbances of the functional state of antioxidant and monooxygenase systems as well as humoral area of the systems of immune protection in pathogenesis of the given disease. It is shown that most components of enzymatic and nonenzymatic antioxidant system (superoxide dismutase, catalase, glutathione peroxidase, restored glutathione, phospholipids) are considerably inhibited by the toxin effect. At the same time content of ceruloplasmin is increased in the blood plasma. Considerable disturbances are also observed in the humoral chain of the immune system (content of immunoglobulins and circulating immune complexes varies) and in the processes of microsomal oxidation.