Tumour necrosis factor (TNF) alpha inhibitors such as infliximab are becoming more widely used for the treatment of selected patients with Crohn's disease, rheumatoid arthritis, and other inflammatory disorders. TNFalpha inhibitors increase the risk of serious infections, including tuberculosis. Screening for and treatment of latent tuberculosis infection before infliximab therapy reduces the risk of developing active tuberculosis. New blood tests that measure interferon gamma production are an alternative to traditional tuberculin skin testing and offer some significant advantages over skin testing for screening of latent tuberculosis infection.