Aim: To determine the characteristics of metabolism in rats of different ages exposed by sodium nitrite with underlying tobacco intoxication. Materials and Methods: The experiments were conducted on male white rats kept on a standard vivarium diet. The rats were divided into three age groups: sexually immature with a body weight of 60–80 g (3 months old), sexually mature with a body weight of 180–200 g (12 months old), and elderly with a body weight of 300–350 g (18 months old). The animals received a single intragastric dose of sodium nitrite via a probe in the form of an aqueous solution at a dose of 45 mg/kg body weight, which is 1/4 of the LD50. The study was conducted 24 and 72 hours after exposure to this toxicant. Results: It has been established, that during the whole experiment, after the affection of the rats, the hyperproduction of active forms of oxygen is present. Simultaneous exposure of rats to sodium nitrite and tobacco intoxication leads to increased generation of active oxygen species by neutrophil granulocytes in the blood. By the end of the experiment, sexually immature rats showed a maximum increase in the content of TBK-active products in all organs (in the liver – 3.3 times, in the kidneys – 3.6 times, in the lungs – 4.3 times, myocardium – 6.0 times). At the end of the experiment, the content of methemoglobin in the blood of young animals after exposure increased significantly (2.6 times). The simultaneous effect of sodium nitrite and tobacco smoke causes disturbances in the antioxidant system. Suppression of superoxide dismutase activity in the blood serum and liver of rats of all age groups was detected. Suppression of superoxide dismutase activity was detected in the blood serum and liver of rats of all age groups. By the end of the experiment, ceruloplasmin content had increased in the group of sexually immature rats, exceeding the level in control animals by 2.4 times at the end of the experiment. Glutathione levels decreased in the liver, lungs, kidneys, and myocardium of rats of all age groups, most significantly in sexually immature rats. At the same time, nitrooxidative stress developed, as evidenced by an increase in nitrite ion levels in all organs during the experiment. After exposure to sodium nitrite, rats of different ages that had been poi soned with tobacco smoke for 45 days showed a significant increase in enzyme activity in their blood serum (alanine aminotransferase activity in blood serum increased 7.7 times, aspartate aminotransferase 5.0 times, lactate dehydrogenase by 1.8 times, gamma-glutamyl transpeptidase by 4.1 times, and alkaline phosphatase by 3.6 times. Secondary endogenous toxins accumulated in the affected organism – medium-weight molecules, the content of which in blood serum was highest at the end of the experiment in sexually immature rats. The myocardium of elderly rats was most sensitive to the action of toxicants. In the lungs of sexually immature and aged rats, cytochrome oxidase activity decreased 1.4 times at the end of the experiment. Microscopic examination of organs revealed that structural reorganization of lungs, liver, kidneys, myocardium of the animals of all age groups was characterized by changes in vascular bed, main morpho functional components (acini, hepatocytes, nephrons and muscle fibers of the myocardium). Conclusions: Exposure of rats of all age groups to sodium nitrite and tobacco smoke causes intensification of free radical oxidation processes in the rats’ bodies, manifested by the occurrence of oxidative and nitrooxidative stress, activation of lipoperoxidation and oxidative modification of proteins, suppression of the antioxidant system, energy supply processes, formation of endogenous intoxication, and increased intensity of inflammatory processes in the body. The most pronounced metabolic changes with underlying nitrite-tobacco intoxication were evidenced in the immature rats that were proved by the experimental data. The identified violations lead to severe intoxication of the body, which requires the additional introduction of corrective factors.