Tuberculosis (TB) has long been one of the world’s great killers. Now, forms of drug-resistant TB--multidrug (MDR) and extensively drug-resistant (XDR)--are occurring at an ominous and accelerating rate. To help in the fight against drug-resistant TB, the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, has formulated an MDR and XDR TB research agenda.