[en] A biochemical indicator of post-irradiation injury recording the increased excretion of metabolites of nucleic acids in the urine of whole-body irradiated cattle in the first 6 to 12 hours after exposure was elaborated. The test consisted in determining deoxycytidine substances by means of thiobarbituric acid after the previous separation by the ion exchange chromatography. A significant increase in the excretion of deoxycytidine substances which was proportional to the radiation dose and made it possible to group the irradiated cattle into animals showing light, medium, and severe forms of the irradiation sickness was found. (author)