Since the beginning of the use of anti-TNF in the treatment of rheumatoid arthritis and other inflammatory diseases, cases of pulmonary tuberculosis and extrapulmonary tuberculosis have been reported in patients receiving such treatment. In most cases, the disease develops by the time the patient has received the sixth infusion. Every patient should be evaluated for latent tuberculosis infection prior to the use of a TNF inhibitor. However, the diagnosis of latent tuberculosis infection is a challenge. The tuberculin test, which was the only test available to detect latent tuberculosis infection for nearly a century, presents a number of limitations. Tests based on the detection of the in-vitro production of IFN-gamma by mononuclear cells activated by specific antigens appear to be more accurate and have been studied in patients with rheumatoid arthritis.