The aim of the work is to analyze the efficiency of using enzyme-linked immunosorbent assay in the diagnosis of cattle leukemia when carrying out health-improving measures in livestock enterprises that are unfavorable for this disease. Indicators of infection of cattle with leukemia virus on 6 farms of agricultural enterprises of the Tomsk region are presented. For serological diagnostics, the immunodiffusion reaction and enzyme immunoassay were used. It has been established that while carrying out health-improving measures in enterprises unfavorable for leukemia in cattle, the use of enzyme-linked immunosorbent assay for serological diagnosis of the disease enabled to identify a greater number of seropositive animals in comparison with a low-sensitivity immunodiffusion reaction. With a decrease in the herd infection rate to single cases of detection of animals infected with the leukemia virus at the final stages of rehabilitation of the enterprise, the number of additional seropositive animals detected by enzyme immunoassay increases. In the final period of herd recovery, the number of animals with a low level of antibodies to the leukemia virus, inaccessible to detection by immunodiffusion, increases. The use of an expensive and labor-consuming delivery of an enzymelinked immunosorbent assay to detect antibodies to the cattle leukemia virus is advisable at the final stages of an enterprise’s recovery. This enables to identify animals with a low level of antibodies to the leukemia virus, to speed up the negative result of a serological test of the entire herd and to exclude repeated outbreaks of infection of animals with this virus in a rehabilitated enterprise.