Recent nosocomial outbreaks of tuberculosis have increased concern about the occupational acquisition of tuberculosis by health care workers. The Centers for Disease Control and Prevention (CDC), Department of Health and Human Services, and the Occupational Safety and Health Administration, Department of Labor, have issued recommendations and regulations in an effort to decrease health care workers' risk for exposure to patients with infectious tuberculosis. Within the CDC, the National Center for Infectious Diseases, the National Center for Prevention Services, and the National Institute for Occupational Safety and Health collaborated to produce the 1994 Guidelines for Preventing the Transmission of Tuberculosis in Health-Care Facilities. As stated in the Draft Guidelines, the major components of health care worker protection from Mycobacterium tuberculosis infection include administration or source controls, engineering controls, and respiratory protective devices. We review the evolution of the seemingly conflicting recommendations for respiratory protective devices made by these Centers of the CDC and explain how the recommendations in the current CDC Guidelines were reached.