Abstract <p>Ozone therapy is a highly effective rehabilitation methodin various pathologies, whose effects may be due to its influenceon the mechanisms of blood oxygen transport. The aim of this studywas to investigate the effects of ozone at different concentrationson the oxygen-transport function of blood, the levels of 2,3-diphosphoglycerate(2,3-DPG) and adenosine triphosphate (ATP), and the gasotransmitter system(nitric oxide and hydrogen sulfide) in rats. The experiment wascarried out on male outbred white rats (<i>n</i> =56), divided into 4 groups: a control group administered with 1.0mL of 0.9% NaCl solution intraperitoneally for 10 days, and threeexperimental groups receiving 0.9% NaCl solution with ozone concentrationsof 1, 10, and 100 µg/kg body weight, respectively, for 10 days.Parameters of the oxygen-transport function of blood, as well asblood levels of 2,3-DPG, ATP, nitrates/nitrites, and hydrogen sulfide,were determined. In animals treated with ozone at a concentrationof 10 µg/kg, an increase in pO₂, sO₂,p50_real, 2,3-DPG, ATP, and gasotransmitters(nitric oxide and hydrogen sulfide) was observed compared to controls.No changes in the oxygen-binding properties of blood were notedat minimal or maximal ozone concentrations. The observed effectof ozone (at a dose of 10 µg/kg) on the oxygen-transport functionof blood in rats, manifested as a decrease in hemoglobin affinityfor oxygen, is mediated by an increase in nitric oxide and hydrogensulfide, which promote the rise in the levels of such modulatorsas 2,3-DPG and ATP.</p>