Gene 15 (UL 45) is 659 bp in length and positioned in 21,146 to 20,487 bp in the genome of EHV-1 Ab4p, which genes contain 219 codons with Mr 23,798 KD. The product is regarded as virion tegument. Some researchers deleted gene 15 (UL45) in RacL11 and in RacH strains of EHV-1 and found that this gene is non essential for virus replication in culture cells. Our recent study analysis of the genomic sequence of Equine herpesvirus 9 which is a closely related to EHV-1 but has stronger neurovirulence than EHV-1 indicated that the identity of gene 15 between EHV-9 and EHV-1 is only 88% in spite of greater than 92% of other most genes. At the present study we reported that the nucleotide sequence of agene 15 is highly conserved in six Japanese strains and three exotic strains which vary in virulence from non virulent to low virulent and virulent.