Abstract: To study CTL epitopes in EIA attenuated vaccine, cDNA sequences encoding majority region of classical MHC class I from 5 horses were amplified by RT-PCR and analyzed. The amplified cDNA fragments included the polymorphic peptide binding region, the more conserved regions of alpha 3, transmembrane domain and cytopasmic domain. The RT-PCR products were synthesized from total RNA of PBMC and then cloned into pMD-18T vector.21-23 clones from each horse were randomly picked up for DNA sequencing. These sequences were further analyzed for their alleles. Our data revealed that each clone contained 3-5 alleles, which indicated there were at least 2-3 loci in MHC class I in horse genome.This results were consistent with the published data of other researches. In addition, the expression variation of classical MHC I alleles between each individuals were different. There was no identical or highly similar allele among horses No.6, No.7 and No.10. The other animals had at least one allele that shared all or more than 98% of nucleotide sequence when compared each other(data not show). These results not only provide fundamental information for our on-going study on CTL epitopes and EIAV-induced immune responses, but also served as important data for polymorphic analysis of horse classic MHC class I in China.