The first phase in the history of the chemotherapy of infection by HIV has been completed. An effective compound, AZT, has been identified that prolongs life and reduces morbidity. The next phase will be to determine the most effective and least toxic regimens of AZT and the patient populations who will most benefit. This phase will also involve the identification and evaluation of additional drugs. The most compassionate way to evaluate these drugs will be expeditious and systematic study rather than ad hoc administration and anecdotal observation. Advances in the chemotherapy of HIV infection are urgently needed. These advances will require new compounds, and because of probable drug toxicity, especially for chronic suppressive therapy, investigation must include examination of regimens that involve drug cycling and combinations.