Abstract
The frequencies of B-alleles in RDM were analysed in samples of 637 bulls born in 1963–64–65, 794 bulls born in 1960–61–62 and 1226 cows from common herds. Among the 46 distinct alleles for which frequencies were estimated only about 10 alleles have frequencies above 1 %. The frequency of some alleles shows consistent variations during the last 10–15 years. The degree of homozygosity at the B-locus has remained almost constant among bulls during the last 10–15 years, while the homozygosity among cows from common herds shows a decreasing tendency.