Purpose of the work: the ability to increase the effectiveness of comprehensive treatment of patients with stomach cancer by individualization based on the definition of carcinogenesis indicators of the malignant process. Materials and methods: 80 patients with stomach cancer were examined, who were identified by MSI on loci VAT 25; VAT 26, the proliferation index of Ki-67 and the p53 gene mutation. The frequency of wild and mutant variants of the p53 gene was studied according to statement of the VAT 25 ta VAT 26 genes stability. In order to assess the prolefethative potential of cells in stomach cancer, the tumor tissue studied the expression of Ki-67, depending on the presence of instability of microsatellites in the loci VAT 25 ta VAT 26. The level of proliferation activity was also assessed depending on the presence of a p53 mutation. Results: The presence of MSI in tumor cells on the locus of VAT 25, there was in most cases a wild version of the gene p53. The absence of MSI according to these loces, the p53 mutation was observed more often. When comparing the differences between them, there were found that in the absence of MSN on VAT 26, the ratio between the absence of a p53 mutation and its presence was reliably different from the ratio of instability. That is why, this can be argued that in stomach cancer mutation of the p53 gene was observed mainly in tumors with the absence of MSN on loci VAT 25 ta 26. Conclusions. And now has been proven, that the data suggest that there are a multifaceted genetic disorder in carcinogenesis. In tumors with preserved function of stability genes, that is why, with the possibility of restoring chromosomal breakdowns, the occurrence and proliferation of malignant cells is associated with the violation of apoptosis at critical points in the process of cell division. In this case, this realize due to the impossibility of mutant form of the p53 gene to synthesize the necessary quarter configuration of the corresponding protein with the latter’s continued inability to stop the process of DNA replication. In this topic has been established that the mutation of the main control gene leads to loss of control over DNA and can contribute to the emergence of a malignant cell, and further loss of cell differentiation is caused by other factors. Furthermore has been revealed that the proliferative activity of swollen cells in stomach cancer has a clear association with the instability of microsatellites on both studied loca of chromosomes.