This article focuses on tuberculosis (TB) and Mycobacterium avium complex (MAC), as these are the most important of the mycobacterioses in HIV-infected patients. It is estimated that in 1999, HIV-related TB reached 1000000 cases and caused 30% of the 2500000 AIDS-related deaths. In HIV-infected patients, TB may have unusual clinical features and can cause diagnostic difficulties. Despite the effectiveness of modern short-course treatment, mortality due to HIV-related TB remains high both during and after treatment. While highly effective therapy exists for both HIV and TB, concomitant administration is fraught with difficulties and many physicians delay HAART for 2 or more months to minimise the risk of toxic side effects. Patients with CD4 counts <50 cells/micro l should receive MAC prophylaxis. Clarithromycin or azithromycin are the preferred agents.