Severe acute respiratory syndrome (SARS) is a threat to healthcare workers. After a brief, unexpected exposure to a patient with SARS, 69 intensive-care staff at risk for SARS were interviewed to evaluate risk factors. SARS developed in seven healthcare workers a median of 5 days (range 3–8) after last exposure. SARS developed in 6 of 31 persons who entered the patient’s room, including 3 who were present in the room >4 hours. SARS occurred in three of five persons present during the endotracheal intubation, including one who wore gloves, gown, and N-95 mask. The syndrome also occurred in one person with no apparent direct exposure to the index patient. In most, but not all cases, developing SARS was associated with factors typical of droplet transmission. Providing appropriate quarantine and preventing illness in healthcare providers substantially affects delivery of health care.