Tuberculosis remains a significant infection in the United States and around the world. Patients infected withMycobacterium tuberculosis can have an asymptomatic infection that can be persistent (latent tuberculosis infection), progressive primary disease, or—years (even decades) later—a reactivation leading to active disease. In most cases, tuberculosis is transmitted from patients with pulmonary or laryngeal disease through airborne droplet nuclei. Prevention of tuberculosis is based on detection of cases, airborne isolation in appropriate negative pressure rooms, respiratory etiquette, use of N95 respirators, and early and complete treatment of tuberculosis cases based on susceptibility testing. Patients with active tuberculosis must be treated for long periods. Many persons infected withM. tuberculosis have no signs and symptoms and are said to have latent tuberculosis infection. The tuberculin skin test and the interferon gamma release assays can be used to diagnose latent tuberculosis infection. Persons with latent tuberculosis infection may warrant treatment to prevent the development of active disease.