The peripheral blood leukocytes in normal subjects were cultured according to Moorhead with addition of CS2 (0,75 microliter/ml of culture). It has been found that CS2 decreases the mitotic index, and in some cultures inhibits totally the cell division. Moreover, it causes structural disturbances of chromosomes being of pre- and postreplicative character as well as their viscous degeneration, lesser spiralization and sometimes pulverization. The presence of greater amount of erythrocytes of the donor's blood in the culture markedly diminished the intensity of these changes.