The results of familial population analysis of stomach cancer and multiple primary malignant tumors (MPMTs) are presented. The data obtained provide evidence for the multifactorial nature of stomach cancer. Hereditary factors accounted for 32% of the general predisposition of individuals to stomach cancer. The age-related character of stomach cancer was established. Genetic heterogeneity of this tumor is suggested by the data obtained. Significant genetic commonness in the inheritance of stomach, colon, Genetic Analysis and Prognosis for Malignant Tumors in breast, endometrial, and ovarian cancer in families of MPMT patients was demonstrated on the basis of the obtained genetic correlations between tumor types in MPMT patients and solitary tumors in members of their families. The greatest genetic load was shown for families of MPMT patients, as compared with families of patients with solitary tumors, the coefficient of MPMT inheritance being equal to 77.4%. The data on the genetic character of stomach cancer and MPMT formed the basis for the identification of criteria for developing methodological approaches to the screening of individuals from risk groups to facilitate early diagnosis and prevention of cancer.