The optimal treatment for HIV infection and the prevention of CMV disease has not been identified. Currently available antiretroviral therapies are hampered by both significant toxicities and the development of resistance. In addition, agents for preventing CMV disease, such as oral ganciclovir, are complicated by poor bioavailability and decreased compliance secondary to toxicities. Moreover, discordant results have been reported regarding the effectiveness of oral ganciclovir for preventing CMV disease. There is a need for newer agents with anti-HIV and anti-herpesvirus activity that have good pharmacokinetic and safety profiles and that will be well tolerated by patients. Adefovir dipivoxil is an oral pro-drug of PMEA, a nucleoside analog with activity against a broad spectrum of retroviruses and herpesviruses, including important human pathogens, such as HIV-1, HIV-2 and CMV. Due to its anti-HIV and anti-herpesvirus activity, adefovir dipivoxil may be able to decrease the incidence of opportunistic herpesvirus infections and prolong survival in patients with advanced HIV infection.