Lipids which enter the composition of actively transcribed and repressed chromatin fractions are found to undergo a peroxidation. The peroxidation induction results in a depression of the endogenous DNA polymerase activity of these fractions. Tetrachloromethane increases the intensity of lipid peroxidation processes and induces a more marked depression of the DNA polymerase activity in all repressed chromatin fractions. It is assumed that selective action of tetrachloromethane on the studied indices of this chromatin fraction may be related to the differences of lipid composition of actively transcribed and repressed chromatin.