Part one of the note reviews relevant scientific data about AIDS. Part two examines the potential liability of physicians to at-risk third parties for failing to warn them about the risk of acquiring an HIV infection. The common law of negligence for failure to prevent exposure to infectious or contagious diseases and for failure to exercise reasonable care to protect a foreseeable victim from danger is discussed. Liability for failure to comply with statutory duties to report communicable diseases to local health authorities is also considered. Part two then considers the element of proximate cause in an action for failing to warn third persons of the risk of HIV infection. The defenses of contributory negligence, comparative negligence, and assumption of risk are reviewed. Two groups of potential plaintiffs are examined throughout the analysis: sexual contacts of patients with HIV infection; and health workers caring for HIV-infected patients. Part three addresses the possibility that physicians who warn third parties may then be liable for failure to maintain patient confidentiality. Part four advises physicians, administrators, and health care attorneys of various measures they may take to minimize the possibility of liability for disclosure or nondisclosure. The note concludes with a discussion of the need for legislative action to guide physicians regarding their legal duty to third parties who are foreseeably at risk of acquiring HIV infection from AIDS patients. 142 references.