More than 6000 samples of 18 different Hungarian sheep breeds were genotyped for 10 unlinked microsatellite loci. After data cleaning, 5434 sheep remained in the analysis. Some locus-breed combinations show deviation from Hardy-Weinberg equilibrium, possibly due to null alleles or theWahlund effect. All breeds show high genetic variability; the lowest expected heterozygosity is that of the British Milksheep (He = 0.588). The Transylvanian Zackel has the highest expected heterozygosity (He = 0.790). It is also the least differentiated breed (Fst = 0.020). Pairwise genetic distances among breeds range from 0.021 between Hungarian Merino and both Mutton Merino and Transylvanian Zackel to greater than 0.105 between British Milksheep and all other breeds. The three Zackel populations - white, black, and Transylvanian Zackel - show small genetic distances among each other, with pairwise Fst values from 0.030 to 0.058. The Transylvanian Zackel tended to have close relationships to some other breeds too, probably due to its low differentiation. Given the individual genotypic information, a Bayesian analysis assigned individuals to breeds generally correctly.