The results of studying the polymorphism of the BoLA-DRB3.2 gene and identifying the associations of its alleles with mastitis for three Ukrainian breeds are presented: Black-and-White milk (UBW), Red-and-White milk (URW) and White-Headed (UWH). In 162 UBP cows, 28 alleles were detected, six of which were determined with a frequency of over 5% (55.3% in total). The *22 allele is detected more frequently (12%). Four alleles are reliably associated with mastitis: susceptibility - *24 (P<0.05) and *26 (P<0.01); resistance - *13 (P<0.05) and *22 (P<0.05). For 117 URP cows 22 alleles were detected. Of these, seven were detected with a frequency of more than 5% (64.5% in total). The most common allele was *07 (15.4%). Four alleles were found to be significantly sen-sitive to mastitis: *07 (P<0.01) and *08 (P<0.05) are associated with the disease, *22 (P<0.001) and *24 (P<0.05) - with mastitis resistance. In 77 UWH blood samples, 28 al-leles were detected, seven of which had a frequency of more than 5% (for a total of 59.6%). The most common variant in this population was *24 (12.3%). Two mastitis-sensitive alleles have been conclusively established: *22 variant (P<0.05) is associated with resistance and *24 with susceptibility to the disease (P<0.001). Alleles for which a statistically significant association with predisposition to the disease has been established can be used as DNA markers to improve the selection of cattle in order to create herds resistant to diseases, including mastitis