Treatment of AIDS has been directed toward the underlying retroviral infection as well as toward specific opportunistic infections and malignancies that are associated with the syndrome. The most extensively studied drugs are reverse transcriptase inhibitors such as AZT and other nucleoside analogs, including didanosine (ddI) and dideoxycytidine (ddC). The most extensive clinical experience has been achieved with AZT. These clinical trials indicated a decreased incidence of opportunistic infection and increased survival in patients with AIDS. However, AZT treatment is associated with dose-limiting toxicities. Additionally, identification of resistance to AZT has increased the need to test the effectiveness of AZT in combination with other drugs. CD4-IgG is capable of binding to HIV envelope protein (gp120) and inhibiting HIV infectivity in test tube studies. Potential therapeutic benefit in patients with HIV infection may be derived from CD4-IgG.