The complete nucleotide sequence of the DNA polymerase gene of herpes simplex virus (HSV) type 2 strain 186 has been determined. The gene included a 3720-bp major open reading frame capable of encoding 1240 amino acids. The predicted primary translation product had an Mr of 137,354, which was slightly larger than its HSV-1 counterpart. A comparison of the predicted functional amino acid sequences of the HSV-1 and HSV-2 DNA polymerases revealed 95.5% overall amino acid homology, the value of which was the highest among those of the other known polypeptides encoded by HSV-1 and HSV-2. The functional amino acid changes were spread in the N-terminal one-third of the protein, whereas the C-terminal two-third was almost identical between the two types except a particular hydrophilic region. A highly conserved sequence of 6 aa, YGDTDS, which has been observed in DNA polymerases of HSV-1, Epstein-Barr virus, adenovirus, and vaccinia virus, was also present at positions 889 to 894 in the C-terminal region of HSV-2 DNA polymerase.