Purpose: to study the allelofund of blood groups of cattle of different breeds.Materials and methods. 3117 Holstein cows of the black-and-white breed were studied, 848 cows of the Simmental breed, 555 cows of the Hereford breed and 172 cows of the Aberdeen-Angus breed. Blood groups were determined using a hemolysis reaction using mono-specific serum reagents, a suspension of erythrocytes and rabbit complement. Blood groups consist of alleles – a set of antigens inherited concatenated. In total, 12 systems are isolated in the blood groups of cattle. In this study, the EAV system is used, since it has the greatest variety of alternatives.Results. It was revealed that the allelofund of the Holstein black-and-white breed is represented by 44 alleles, the Simmental breed – 87 alleles, the Geford breed - 53 alleles, the Aberdeen Angus breed – 38 alleles. The most common alleles of blood groups of cattle of Holstein black-and–white breed are G2Y2'E'1Q' and I2, Simmental breed – Q', Hereford breed – b and Y1D'I', Aberdeen-Angus breed O1Q'. The frequency of occurrence of these alleles exceeds 6% and in some cases reaches 44%. It should be noted that the most common alleles of breeds remain in the leading positions in frequency of occurrence over time and are not replaced by other alleles. It is also established that in each breed there are specific alleles inherent only to it, which can be called markers of the breed. So, in the Holstein black-and–white breed, these are the alleles O1Y1G'G" and O3J'2K'O', in the Simmental – D'E'3G'I' and D'G'I'Q', in the Hereford – Y1D'I' and I2Y2G'G", in the Aberdeen-Angus – P1Y1 E'3P'2Q'G".