The most common of the 12 known genetic variants of β-casein are A1 and A2. Unfortunately, the A1 allele is linked to a number of diseases in humans. Therefore we should consider whether it is possible to reduce the occurrence of the undesirable allele in milk. Hence the aim of the study was o determine the frequency of the A1 and A2 alleles and the degree of genetic variation in β-casein in cattle of two international breeds (Holstein-Friesian and Simmental) and two local breeds included in a genetic resources conservation programme (Polish Red and White-Backed), raised in Poland. The study was conducted on 386 cows from 29 farms. Genetic variation in the CSN2 gene was determined by PCR-RFLP using the DdeI restriction enzyme. The cattle breeds, especially the White-Backed and Polish Red, were shown to have a relatively high frequency of the A2 allele (over 0.5). In addition, an excess of heterozygous genotypes was observed in all the tested populations, but homozygous A2A2 individuals were clearly predominant in the local breeds.The results show that local cattle breeds are particularly predisposed to produce ‘A2 milk’ and suggest that steps should be taken towards selection of cattle producing milk with the A2 variant of β-casein, which would increase the profitability of its breeding and meet the current requirements of both individual consumers and the medical profession, mainly pediatricians.