Most people infected by TB mycobacteria will not develop active TB as their immune response works to keep the disease dormant. But as a person's immune system weakens, which is what happens with HIV infection, the tuberculosis infection can reactivate. An estimated one third of the 40 million people living with HIV/AIDS worldwide are co-infected with TB. Tuberculosis is now the leading cause of death among people who are HIV positive: without treatment, about 90% of them will die within months of contracting the disease. Current TB drugs negatively interact with ARVs, making co-treatment of TB/HIV co-infected patients very complex. We need to adapt our strategies to face this lethal combination, by offering counseling and voluntary HIV testing to TB patients, by actively screening HIV positive patients for TB and by integrating health services for the two diseases. We also need better tools for diagnosis and treatment of TB in HIV positive patients. Indeed, diagnosis of TB cannot rely on microscopy alone and a more sensitive test is urgently needed so that patients can be started on treatment as early as possible.