When Willy Sutton was asked why he robbed banks, he is said to have answered, Because that's where the money is. If we were to ask my copanelists, Drs. Dooley and Jarvis, why the Centers for Disease Control and Prevention (CDC) has placed such emphasis on tuberculosis isolation rooms and on respirators to be worn in them, they might likewise reply, Because that's where the risk is. Although both answers appear equally logical at first, in my view further analysis shows that Mr. Sutton's rationale has the better foundation. The much debated draft of the Guidelines for Preventing of Tuberculosis in Health-Care Facilities, Second Edition,* published in the Federal Register of October 12, 1993, acknowledged the hazard of persons with unsuspected tuberculosis in its introduction: Transmission is most likely to occur from patients with unrecognized pulmonary or laryngeal TB who are not on effective antituberculous therapy.1 Much of the lengthy document that followed this introduction, however, and nearly all of the ensuing controversy surrounding its recommendations, has focused largely on patient isolation and on the role of personal respirators in protecting those who must enter isolation rooms and other designated high-risk environments. An essential c o m -