OBJECTIVE: Human cytomegalovirus (HCMV) displays genetic polymorphisms. Nineteen open reading frames (ORFs, UL133-UL151) found in the Toledo strain of HCMV and other low-passage clinical isolates may be essential for viral infection. This study aimed to analyze the polymorphism of HCMV UL134 gene in clinical isolates and explore the relationship between the polymorphism and HCMV infection. METHODS: PCR was performed to amplify entire UL134 region in 32 clinical isolates, which had been proven as HCMV-DNA positive by FQ-PCR. PCR products were sequenced. RESULTS: All of the 32 isolates were amplified and sequenced successfully. HCMV UL134 gene was highly conserved in the clinical isolates. UL134 ORF and its predicted protein in the clinical strains displayed 96.4%-98.3% nucleotide identity and 92.7%-94.9% amino acid identity respectively compared to those in the Toledo strain. A new posttranslational modification site, sulfationcamp (SUL) site, was found in UL134 protein of all of the clinical isolates except 35j. CONCLUSIONS: HCMV UL134 gene in clinical isolates was highly conserved. No substantial relation was found between UL134 gene and HCMV infectious diseases. ［Chin J Contemp Pediatr, 2007, 9 (6):583-586］