The rate of proteins oxidative modification of chromatin in the liver and Heren's carcinoma of rats was studied. It was shown that the tumour development was accompanied by the changes of histones and nonhistones carbonyl derivatives levels both in the tumour, and in the liver. The processes of free-radicals oxidation of researched proteins are sensitive to the fortnight introduction of 5,6-benzcumarine-5-uracil and natural herbs preparation, resulting in the inhibition of tumour development.