The article presents the results of testing by blood groups of animals of the Holstein breed of German and Dutch breeding, as well as the descendants of the first generation in the herd of Joint-Stock Company "Aydyn". According to the EAC locus, the most common antigens are C2, E, R2, X2, L′, which characterize the population of the analyzed animals and the Holstein breed in general. In the allele pool of the EAB locus, 61 alleles were identified in the population of the descendants of the first generation, 33 alleles in the population of German breeding, and 13 alleles in Dutch breeding. In the analyzed populations of German breeding and the descendants of the first generation, 18 identical alleles were identified. The main specific weight in the structure of the allele pool is occupied by the alleles B2O1, B2O1Y2D′, G2Y2E'2Q′, I2, O1, DʹGʹQʹ, Q′, and G″. Alleles B2G2Y2IʹOʹYʹ, O2Y2Jʹ2Oʹ, O2DʹGʹ, Y2DʹEʹ3GʹOʹPʹQʹYʹBʺGʺ and O2Jʹ2Oʹ are specific for the descendants of the first generation. The daughters of the bull Form - carriers of the allele I2 - had an advantage in milk yield over the peers of the daughters Kiperush 79 per 592 kg of milk, the difference is significant (P<0.05).