The antiviral activity of 1-beta-d-arabinofuranosylcytosine (ara-C, cytarabine, Cytosar), 5-iodo-2'-deoxyuridine (IdUrd), 9-beta-d-arabinofuranosyladenine (ara-A), and disodium phosphonoacetate (PAA) have been compared in herpes simplex virus type 2 (HSV-2)-infected primary rabbit kidney cells and in female hamsters with genital HSV-2 infection. In vitro, ara-C and IdUrd were more active than ara-A, and PAA was least active. In female hamsters with genital HSV-2 infection, intravaginal treatment with PAA or ara-A was more effective than either ara-C or IdUrd. PAA was more active than ara-A when treatment was initiated early (1 h) after infection. The activity of PAA was greatly reduced if initiation of treatment was delayed for 24 h. Both PAA and ara-A reduced the virus titers of the vagina and protected hamsters from death when the drugs were given by either the intravaginal or subcutaneous route, with intravaginal treatment being more effective.