The article solves a current task concerning a substantiated use of acetylation phenotype as susceptibility biomarker to unfavourable effect of chemical substances in scientific studies. Objective: to study a combined effect of sodium nitrate and cadmium chloride on the prooxidant-antioxidant balance of the blood, liver and functional state of the central nervous system in young rats with different acetylation type. The experimental studies were performed on immature male rats 1,5-month of age. The experimental animals were divided into two groups according to the amount of general sulfadimine excreted with urine: "rapid" and "slow" acetylators. 2 subgroups were differentiated in every group: I - control animals, II - animals subjected to administration of cadmium chloride and sodium nitrate. Administration of sodium nitrate and cadmium chloride to animals in the doses 1/15 DL50 and 1/150 DL50 respectively during 14 days found that at the young age "slow" acetylation type is susceptibility marker, and the criteria of a harmful effect in them are the following: 25% increase protein peroxide oxidation in the blood plasma, 34% and 30% increase of average molecular peptides and ceruloplasmin respectively, and 6,7 times increase of methemoglobin (hemiglobin) concentration. Nitrate-cadmium intoxication caused inhibition of the integral behavioural activity both in slow and rapid acetylators. Disturbed behavioural activity in young animals with "slow" acetylation type under conditions of subacute effect of sodium nitrate and cadmium chloride is caused mainly by an increased content of liver lipoperoxidation secondary products and less - by the levels of average molecular peptides and ceruloplasmin in the blood plasma, and in "rapid" acetylators - by increased products of oxidation-modification proteins.