The sequence of guinea pig cytomegalovirus (GPCMV) was determined by direct sequencing of salivary gland homogenates obtained following sustained, serial in vivo passage of pathogenic virus in guinea pigs. The 233,501-nucleotide salivary gland (SG) genome was noted to have 11 differences compared to the tissue culture-passaged virus, although no variations were noted in putative protein coding sequences.