Using cytometry and an microfluorimetry, we have determined the genome size in Chinese hamster Cricetulus griseus, as well as absolute and relative DNA content of its individual chromosomes and of chromosomes in the transformed Chinese hamster cell lines V-79 RJK and Vebr-5 after prolonged cultivation. It has been shown that the genome size in male and female Chinese hamster is 6.660 and 6.746 pg, respectively. Absolute content of chromosomal DNA of both studied cell lines differed significantly from the content of the corresponding chromosomal DNA of the Chinese hamster normal karyotype. During long-term cellular cultivation, changes in the DNA content of certain chromosomes in both cell lines (generally upward) reached 20-25 %. The level of DNA amplification in the p-arm of chromosome Z6, registered at the beginning of the experiment, in the course of further cellular cultivation (over 20 years) remained stable. The data obtained allow us to conclude that the malignant transformation of cells and subsequent adaptation to the conditions in vitro leads to a profound restructuring of its genome, which affects almost all chromosomes.