Objective To investigate the variability of human cytomegalovirus（HCMV） UL138 open reading frame（ORF） in clinical strains.Methods HCMV UL138 ORF was amplified by polymerase chain reaction（PCR） and PCR amplification products were sequenced directly

and the data were analyzed in 19 clinical strains.Results UL138 ORF in all 30 clinical strains was amplified successfully.Compared with that of Toledo strain

the nucleotide and amino acid sequence identities of UL138 ORF in all strains were 97.41% to 99.41% and 98.24% to 99.42%

respectively.All of the nucleotide mutations were substitutions.The spatial structure and post-translational modification sites of UL138 encoded proteins were conserved.The result of phylogenetic tree showed that HCMV UL138 sequence variations were not definitely related with different clinical symptoms.Conclusion HCMV UL138 ORF in clinical strains is high conservation

which might be helpful for UL138 encoded protein to play a role in latent infection of HCMV.