The dynamics of the endogenous production of NO metabolites, nitrites, nitrates, and volatile nitrosamines, has been investigated in the body, a tumor tissue, and peritoneal macrophages of mice F1 (C57Bl × CBA), Balb/c and BDF with subcutaneously transplanted tumors: Ehrlich carcinoma (EC) and Lewis metastatic lung carcinoma (LC). It has been shown that during the first three weeks, growth of EC is accompanied by a statistically significant increase in the total concentration of NO metabolites (NOx; nitrites + nitrates) up to levels (7.3 ± 3.49) × 10−6−(7.8 ± 2.57) × 10−5 mol/kg in the tumor tissue and a sharp increase in NOx excretion with urine. At the same time, in the LC tumor tissue the maximal level of NOx (3.6 ± 0.46) × 10−5 mol/kg was registered on day 7, and later it decreased demonstrating negative correlation with the tumor mass. At the stage of intensive LC growth (14, 21 days) there was significant inhibition of nitrite secretion by peritoneal macrophages. In all the controlled time-intervals the EC tumor tissue contained carcinogenic N-nitrosodimethylamine and N-nitrosodiethylamine; however, their concentrations significantly varied. Thus, the ability of the tumor tissue to produce NO metabolites was more pronounced in EC than in LC and depended on the time parameters of tumor growth.