The major histocompatibility complex (MHC) plays a central role in the control of disease resistance and immune response. Extensive genetic diversity in MHC genes provides a valuable source for genetic improvement, via selection, in many domestic animals. Exon 2 of the class II MHC, termed Ovar-DRB1 in domestic sheep (Ovis aries), has been suggested as important disease resistance and immune response gene. We characterized Ovar-DRB1 in DNA samples from 138 individuals of a population of the Iranian Sangsari sheep breed using PCR-RFLP.Eight DRB1 alleles were identified among Iranian Sangsari sheep, including one previously unrecognized allele. Eight homozygous genotypes were observed: a, b, c, d, f, g, h and N. Genotype bb was the most common pattern (46 of 138).Heterozygous genotypes (ag, cb, cd, bf, and bN) were also observed. The observed homozygosity and heterozygosity values were 0.6377 and 0.3623, respectively, vs expected values of 0.220 and 0.779. Iranian Sangsari population deviate significantly from the theoretical proportions (FIS= 0.5283; p=0.0005). In conclusion, PCR-RFLP analysis allows rapid identification of Ovar-DRB1 types and discrimination of homozygous and heterozygous genotypes. This study indicates that the exon 2 region of the Ovar-DRB1 gene is highly polymorphic in the Iranian Sangsari sheep breed.