Approximately 10% of new cases of tuberculosis (TB) in the United States occur in HIV-infected persons. HIV infection dramatically increases the risk of TB, and this increased risk is present throughout the course of HIV infection. TB and HIV coinfection complicates the course and treatment of both diseases. Isoniazid preventive therapy and antiretroviral therapy both substantially reduce the risk of developing active disease in persons with latent TB infection. Antiretroviral therapy should be given during treatment for active TB, as mortality was reduced by 56% with initiation of antiretroviral therapy before the completion of TB therapy. In addition, for patients with low CD4+ cell counts (less than 200/microm3), starting antiretroviral therapy during the intensive phase of TB treatment reduced mortality by 34% compared with delaying antiretroviral therapy until 8 weeks after TB treatment initiation.