The Karyotypic structure of some clones and subclones of Chinese hamster cells has been studied (CHO-KI). 60-80% of all the clonal cells demonstrated the identical karyotype (the main structural variant of karyotype - MSVK). The distribution of cells according to the number of chromosomes does not vary within 90 passages of clone cultivation (about 300 cell generations) and 35 passages of subclone cultivation (more than 100 cell generations). In two of three clones the frequencies of cells with MSVK and with additive karyotype variants do not change, while in one clone a long cultivation leads to lowering the frequency of cells with MSVK and to growing the frequency of cells with other karyotype variants. Recloning does not lead to decreasing the karyotypic heterogeneity of clonal populations. The distribution of clonal cells according to the deviation from the modal number of chromosomes is closely related to the Poisson distribution, while the distributions of cells from two clones with the stable karyotypic structure according to the number of greater structural greater deviations from MSVK are related to a degeneration Poisson distribution. Different chromosomes are involved in karyotypic changes in variable proportions, and the frequencies of cells with simultaneous deviations in various chromosome groups are in most instances higher than frequencies expected in the case of independent deviations. The reasons of stability of karyotypic structure in clonal populations is discussed.