One hundred and thirty-seven patients of advanced pulmonary tuberculosis were randomly allocated to receive metronidazole 400mg tid (76) or placebo (61) for 2 months in a single blind study. All received streptomycin 0.75 g,INH 30 mg and rifampicin 450 mg daily as standard antitubercle treatment. There were no significant pretreatment differences, among both groups. Compared to placebo group there was superior clinical improvement in metronidazole treated group at 4 and 8 weeks (81% vs 53%-P less than 0.05; 87% vs 72%-P less than 0.05 respectively), greater sputum reduction at 4 weeks (49% vs 9%-P less than 0.001) greater radiologic improvement at 4 weeks (60% vs 43%-P less than 0.01) and a better antituberculous drug sensitivity. Metronidazole seems to have beneficial adjuvant role in the drug treatment of tuberculosis. This may improve response in advanced cases.