During the decade since the World Health Organization declared tuberculosis a global health emergency, the problem has worsened despite a vaccine and an effective treatment for infections, because of poverty, social inequality, and the growing AIDS epidemic. Scientists in a wide range of medical and biological disciplines from around the world report on what is now known about the disease, extending Barry Bloom's classic 1994 Tuberculosis: Pathogenesis, Protection, and Control. They look at the current situation, clinical and epidemiological features, diagnosis, and therapies in the first section. Then they turn to the bacillus itself, M. tuberculosis, considering its genetics, genomics, cell structure, and metabolism. The final section explores the interaction of the bacillus with its host, beginning with its entry and survival in its primary residence, a macrophage.