The levels of tissue antioxidant uric acid in relation to chromosomal aberrations and leaving erythrocytic chromatin were determined in the spleen, bone marrow and blood of rats exposed to toxic hyperoxia (0.7 MPa O2, convulsions). Considerable growth of the uric acid levels and the rate of chromosomal aberrations in all tissues was observed within the first hours after treatment. The article discusses mechanisms of uric acid formation, redistribution and disintegration in tissues under extreme conditions. Specificity of the uric acid metabolism in tissues was shown with the help of the correlation analysis of uric acid concentrations. Inverse relationship between uric levels and chromosomal impairments noted in some cases permits to make a supposition about genoprotective properties and adaptogenic role of uric acid during oxidative stress.