The proposed study aims to determine the optimal time to initiate HAART (defined as d4T + 3TC + efavirenz) in previously untreated HIV-infected adult patients with TB and low CD4 cell counts. The study is a multicentre prospective, randomized, open-label two-armed trial with no placebo. It is designed as a superiority trial to compare the "early arm" (HAART initiated 2 weeks after TB treatment onset) with the "late arm" (HAART initiated 2 months after TB treatment onset). Efficacy will be assessed by the survival rate in the two arms. Secondary objectives will include evaluation of (1) the safety of an early initiation of HAART in terms of drug interactions or paradoxical reactions, (2) the occurrence of opportunistic infections diagnosed during the follow-up period, (3) patients' adherence to TB treatment and HAART, (4) the rate of hospitalization for any cause during the trial; the measure of (5) the effectiveness of the TB treatment and HAART and (6) the predictive factors for the survival, the response to anti-TB therapy and HAART and the paradoxical reactions.