The major objective of this proposal is to provide a resource for the continuing evaluation of antiviral chemotherapeutic agents in experimental animal infections which are models of human herpesvirus diseases. The investigations of a new antiviral compound provided by the Antiviral Substances Program of NIAID include: 1) a determination of the in vitro activity of the drug against appropriate representative viruses in both mouse and human tissue culture cells, and 2) an evaluation of the efficacy of the compound in the treatment of appropriate experimental viral infections in animal models of herpes simplex virus and cytomegalovirus infections.