The primary goal of antiretroviral therapy for human immunodeficiency virus (HIV) infection is suppression of viral replication. Evidence indicates that the optimal way to achieve this goal is by initiating combination therapy with two or more antiretroviral agents. The agents now licensed in the United States for use in combination therapy include five nucleoside analog reverse transcriptase inhibitors (zidovudine, didanosine, zalcitabine, stavudine and lamivudine), two nonnucleoside reverse transcriptase inhibitors (delavirdine and nevirapine) and four protease inhibitors (saquinavir, ritonavir, indinavir and nelfinavir). Current recommendations suggest that antiretroviral therapy be considered in any patient with a viral load higher than 5,000 to 20,000 copies per mL, regardless of the CD4+ count. Selection of the combination regimen must take into account the patient's prior history of antiretroviral use, the side effects of these agents and drug-drug interactions that occur among these agents and with other drugs as well. Because of the potential for viral resistance, nonnucleoside reverse transcriptase inhibitors and protease inhibitors should only be used in combination therapy. Antiretroviral agents are rapidly being developed and approved, so physicians must make increasingly complex treatment decisions about medications with which they may be unfamiliar.