HIV-infected patients are at high risk for herpesvirus infections, including varicella-zoster virus ( VZV ) infections, also called shingles. Acyclovir, an approved drug, is widely used to treat VZV infections in the HIV population. Since no data from controlled studies are available to define the role of antiviral therapy for VZV infections in HIV-infected patients, a study is needed to test the relative efficacy of brovavir, an experimental antiviral drug, versus that of acyclovir.