The DNA polymerase activity in BHK 21/C13 cells infected with pseudorabies virus is inhibited by incubation with antiserum to pseudorabies but not by incubation with pre-immune serum or by antiserum to herpes simplex virus type 1 (HSV-1) or herpes simplex virus type 2 (HSV-2). It also differs from the cell enzyme and the enzymes in HSV-1 or HSV-2 infected cells in its requirement for KCl in the in vitro assay. It seems likely, therefore, that pseudorabies virus specifies its own DNA polymerase.