In July 1990, the federal Centers for Disease Control (CDC) reported the first case of possible transmission of the Human Immunodeficiency Virus (HIV) to a patient from an HIV-infected health care worker. The transmission may have occurred during an invasive dental procedure performed on her by a dentist who had AIDS, and in January 1991, the CDC reported possible HIV transmission during dental procedures to two other patients of the same dentist. Further, the recent revelation that a respected surgeon at a major medical center performed many surgical procedures while infected with HIV created substantial public concern. These cases call into question the prudence of allowing infected workers to continue performing medical and dental procedures that involve some risk, however slight, of transmitting HIV infection to patients. Whether HIV-infected workers should be excluded from practice of their profession because of a remote risk to patients relates directly to levels of tolerable risk in health care delivery and in social policy.