Approximately 700 men and women ≥ 18 years of age with documented HIV infection and smear-positive pulmonary TB patients will be enrolled. Eligible TB/HIV co-infected patients will be offered antiretroviral therapy (ART), starting at one of the three time points listed above through the CAPRISA AIDS treatment programme which includes extensive counselling and adherence support. The study participants will be followed for 18 months to assess the primary study endpoint of the optimal time to start antiretroviral therapy (ART) in patients on tuberculosis (TB) treatment by comparing clinical status (CD4+ cell count, viral load, opportunistic infections.