The epidemic of infection with the human immunodeficiency virus (HIV) and the acquired immunodeficiency syndrome (AIDS) poses a major ethical question: How can we control the epidemic and the harm that it causes without unjustly discriminating against particular social groups and without unnecessarily infringing on the freedom of individuals? This question pertains to three spheres of public policy in the United States: public health, the delivery of health care, and research. In the public health sphere, vigorous educational efforts will be required, as will modified approaches to intravenous drug use, prostitution, and homosexual and bisexual sexual activity. Carefully targeted, voluntary testing and screening programs should be coupled with counseling and with guarantees of confidentiality and nondiscrimination where these are appropriate. Both health care workers and the health care system have a moral obligation to provide care to people with HIV infection, but heroic self-sacrifice should not be required provided that infection control precautions are observed. Patients with neurological involvement and terminally ill patients will benefit from statutes allowing recognition of advance directives about preferred modes of care or nontreatment. There is a moral imperative to perform intensive research directed toward the understanding, treatment, and prevention of HIV infection and AIDS. The research process will raise challenging ethical questions.