SUMMARYDNA polymerase activity present in Trichoplusia ni multiple nucleocapsid nuclear polyhedrosis virus-infected Spodopterafrugiperda cells has been analysed by chromatography on DNA-cellulose and phosphocellulose columns. In infected cells a new fraction of activity was found to bind to the columns more strongly that did polymerase activity in uninfected cells. The infected-cell-specific DNA polymerase was purified by a combination of DNA-cellulose chromatography of crude extracts and phosphocellulose chromatography of the semi-purified activity. The final product contained a single polypeptide of molecular weight 126 000 which was not found in uninfected cells. The purified enzyme was inhibited by aphidicolin and [E]-5-(2-bromovinyl)-2'-deoxyuridine triphosphate, but not by bromovinyldeoxyuridine. The enzyme was shown to be an early enzyme, probably a delayed early protein, since it was present in cells inhibited by aphidicolin which were locked into the synthesis of early proteins by the drug.