Adjunctive immunotherapy with heat-killed Mycobacterium vaccae was studied in a randomized; placebo-controlled trial of 120 non-human immunodeficiency virus-infected adults with newly diagnosed pulmonary tuberculosis. Patients were randomised to a single dose of M.vaccae or placebo 1 week after beginning chemtherapy and were followed up for 1 year. M.vaccae was safe and well tolerated. the rate of sputum culture conversion after 1 month of tuberculosis treatment was 35in the M.vaccae group and only 14in the placebo group (P=01) but was comparable at 2 months and thereafter. Patients receiving M.vaccae had greater improvement on chest radiography at 6 months (91) vs. 77for placebo recipients; P=04) and 12 months (94vs. 80; P=04) after initiation of tuberculosis treatment. These data provide evidence of an early increase in sputum culture conversion and greater radiographic improvement among patients who received M.vaccae. Further studies are warranted