Although health care has been practiced for eons and although hundreds of thousands of workers are engaged in it, we know distressingly little about ways to prevent work-related infectious illnesses in this important group. Assumptions may be dangerous and expensive: Are "universal precautions" effective; when are respirators necessary? These kinds of questions have taken on particular urgency in the face of multiple-drug resistant tuberculosis and the spread of human immunodeficiency virus and other blood-borne pathogens. Furthermore, health care has moved from the traditional hospital setting into ambulatory, home, and other noninstitutional settings, thus increasing the complexity of worker protection measures. Steps to ensure the safety and health of health care workers must therefore include research and action that lead to identifying workers at risk; planning; education; providing necessary equipment and assuring adequate staffing; using appropriate techniques and precautions; immunizing workers; appropriately isolating patients; record-keeping; and evaluation. Curricula in schools for health professionals should include material on ways to achieve good health for health care workers. Public health officials and regulators should pay more attention to this arena.