Surgery is the only effective modality in treating gastric cancer (GC); however, this procedure works well only in its early detection. In this regard, oncomarkers are considered to be a promising area in searching for ways to early detect cancer and to select management tactics for patients with this disease. Objective — to evaluate the genetic status of the gastric mucosa in cancer patients and to justify whether the molecular marker systems can be introduced into surgical practice. Material and methods. Three patient groups were formed to search for a molecular marker-based system for the diagnosis of GC, to determine prognostic markers for its progression, and to assess the role of molecular changes in the combined treatment of GC. The original molecular marker system was used. Results. The investigation showed that the determination of RASSF1A and MLH1 gene methylation, MMP7, hTERT, and BIRC5 gene expression, and telomerase activity should be used in combination with other studies for the diagnosis of early-stage GC. The system of predictive markers for recurrent and metastatic GC should include the determination of CDH1, N33, and RUNX3 gene methylation. To improve the results of combined therapy in patients with locally advanced GC, it is advisable to assess molecular factors that determine individual differences in the pharmacodynamics and pharmacokinetics of drugs and that are associated with the course of the disease, prognosis and response to treatment. Conclusion. It has been shown that molecular marker systems can be introduced into surgical practice, by using GC as an example, which will be able to improve the diagnosis, to predict the course of the disease, and to help choose its treatment policy.