Forty-nine AIDS patients, most of who were antiretroviral therapy (ARV) naive, with active tuberculosis, were treated with Rifampin 600 mg, Isoniazid 400 mg and Pirazinamide 2 g daily. They also received ARV, consisting of Efavirenz (600 mg/day) plus 2 NRTIs. All patients were prospectively followed for at least 24 months. Baselines were: male/female ratio 2:1, mean age 34.7 +/- 9.4 yrs; weight 51 +/- 9.0 kg, viral load 5.6 +/- 0.6 logs, CD4 cell count 101 +/- 128 cells/ mm3. Follow up mean values of data logs of VL and CD4+ cell /mm3 counts were: VL 1.7 and CD4+ 265; VL 1.3 and CD4+ 251; VL 1.4 and CD4+ 326 at 6, 12 and 24 months, respectively. Weight gain changes were: 5 +/- 9.9 +/- 12 and 21 +/- 16 kg respectively at 6, 12 and 24 months. A non-concomitant ARV regimen was introduced at least three weeks after TB treatment initiation. Severe adverse reactions included rash (two), toxic hepatitis (six), Immune Reconstitution Syndrome (seven), and four deaths. We conclude that Efavirenz at a daily dose of 600 mg is sufficient and safe to treat HIV/TB patients using a Rifampin containing regimen.