Milk is one of the most valuable human foods. The main protein in milk is casein. The beta-casein gene (CSN2) is responsible for the synthesis of β-casein in cattle. The most common variants of β-casein in dairy cattle are A1 and A2. Option A1 βcasein may also cause type 1 diabetes, coronary heart disease and autism, while option A2 lowers cholesterol and reduces the risk of inflammatory bowel reactions. Analysis of scientific publications indicates that the beta-casein gene (CSN2) has not been studied in the indigenous breeds of cattle of Ukraine, which are carriers of specific gene complexes and most of the rare alleles. The frequencies of different variants of beta-casein in three indigenous breeds of cattle of Ukraine - the Ukrainian gray breed, the Ukrainian whiteheaded breed, the Ukrainian Carpathian brown breed and Ukrainian water buffaloes were investigated. Genomic DNA isolated from animal whole blood was amplified using primers based on the bovine CSN2 gene sequences. Amplified CSN2 fragment 121 bp in length. was treated with restriction enzyme DdeI. The allele and genotype frequencies of the CSN2 gene differ significantly in the studied cattle breeds. The frequencies of the A2 allele of CSN2 vary from 0 to 1.0, and the frequencies of the CSN2A1A2 genotypes from 0 to 0.844 and CSN2A1A1 from 0 to 0.480. The maximum (100%) content of the A2 allele was noted in water buffaloes (Bubalus bubalis), and the minimum in the Carpathian brown breed (the A2 allele is absent), 46.8% in the Ukrainian gray breed, 26% in the Ukrainian whiteheaded breed. The frequency of the A2A2 genotype in all studied breeds, except for the water buffalo (1.0), was low (0.046) in the Ukrainian gray breed, or this genotype did not occur at all. These results can be used to correct breeding programs for breeding the studied native breeds of cattle and water buffaloes in Ukraine.