Following inoculation of chimpanzees, the human immunodeficiency virus (HIV) establishes a long-term persistent infection characterized by seroconversion and the presence in peripheral blood cells of recoverable virus which can be quantitated. Because most HIV-infected chimpanzees have developed no signs of clinical diseases or hematologic abnormalities, their virologic, serologic and other immune responses can be compared with those of asymptomatic HIV-infected persons. This analysis might lead to the identification of factors important in preventing the development of disease. There are now approximately 100 HIV-infected chimpanzees in the United States, and many of these animals could be made available for testing chemotherapeutic agents for the ability to alter virus load or to enhance immune responses.