Major histocompatibility complex genes, also called bovine lymphocyte antigen (BoLA), have received attention because of their association with host immunity. The BoLA gene is located on the short arm of bovine chromosome 23. In the class II region of the BoLA gene, at least 12 loci have been described including in the class IIa region: DRA, DRB1, DRB2, DRB3, DQA, DQA2, DQB1, and DQB2; class IIb region: DYA, DYB, DIB, and DOB. Lewin H. A. (1996) identified 35 DRB3 alleles in exon 2 with a technique described by van Eijk et al. (1992) involving polymerase chain reaction (PCR) and endonuclease restriction fragment length polymorphism (RFLP). The BoLA-DRB3.2 locus is highly polymorphic; more than 54 different alleles have been reported. The BoLA-DRB3.2 alleles potentially affect many traits related to immunity, SCC, and mastitis incidence. Associations have been made with some infectious diseases of cattle and BoLA genes. Others indicated that one BoLA-DRB gene pattern was associated with resistance to Staphylococcus aureus mastitis, BoLA-DRB3.2*8, *16, *22, and *28 alleles were associated with elevated SCC and cows with BoLA-DRB3.2*16 and *24 were more susceptible to IMI caused by major mastitis pathogens. Furthermore, cows with BoLA-DRB3.2*ll, *12, and *23 alleles were more resistant to clinical mastitis and to IMI caused by major mastitis pathogens, however BoLA-DRB3.2 *16 was associated with lower SCS in Holsteins and BoLA-DRB3.2 *23 was associated with severe coliform mastitis. Most of the previous studies of the BoLA-DRB3.2 gene have involved Holstein cows or a combination of various breeds. Few studies have analyzed exclusively the BoLADRB3.2 gene of Iranian Sistani cattle and has not reported frequency of BoLA-DRB3 alleles in Russian Yaroslavl breed. The purpose of the present study was to determine the BoLA-DRB3.2 allele pattern in Iranian Sistani and Russian Yaroslavl breeds.