We analyzed 150 patients with pulmonary tuberculosis from 1990 to 1996 (i) to evaluate the frequency of drug resistance, (ii) to elucidate factors influencing the response to chemotherapy, and (iii) to attempt to improve the therapeutic approach. Multidrug-resistant tuberculosis strains were not found. By univariate analysis, there were 8 factors associated with an increased sputum conversion time: male gender, prior treatment, complications, progressive chest radiographic findings, a high Ziehl-Neelsen stain score, lymphocytopenia, a high erythrocyte sedimentation rate (ESR), and hypoproteinemia. Complications, prior treatment, a high Ziehl-Neelsen stain score, and a high ESR were independent predictive factors in a Cox proportional hazard model. Recursive partitioning and amalgamation (RPA) defined 3 subgroups that responded to treatment. In order to reduce the time to sputum conversion, poor responders according to the RPA should be treated with a 4-drug regimen containing pyrazinamide.