The content was studied of the endogenous intoxication syndrome markers (medium-size molecules) in red cells, blood plasma and urine of patients with grave gestoses in view of the fact that underestimation of the syndrome considered tends to significantly narrow the broadness of pathogenetic notions about the given pathology and to negatively influence the effectiveness of intensive therapy of patients. Besides, the problem gets more complicated because of pathogenetic specificities of severe gestoses (the use of the well-known methods of detoxication is made difficult in the patients). Ozone hemotherapy as an efferent method of detoxication and employment of antioxidant in the complex of intensive therapy of patients with severe gestoses make for lowering the degree of catabolic disturbances by decreasing the level of medium-size molecules in erythrocytes, blood plasma and urine.