BACKGROUND To identify predictive factors of treatment incompletion in elderly patients with newly diagnosed pulmonary tuberculosis. METHODS In elderly patients of more than 65-years old and with newly diagnosed pulmonary tuberculosis, a retrospective study was conducted. A total of 88 patients were admitted in International Medical Center of Japan with pulmonary tuberculosis between June 2000 and February 2002. The relationships between several clinical parameters, including patients' performance status (PS) scale proposed by the Eastern Cooperative Oncology Group, laboratory data, or, radiological findings on admission and treatment incomeletion were assessed by univariate and multivariate logistic regression analyses. RESULTS Ten patients could not complete their treatment; including nine patients who died during hospitalization and one who refused tuberculosis treatment. Preliminary analysis indicated that the treatment incompletion was related with twelve factors including PS. On univariate analyses, 9 factors were associated with incomplete treatment. The best model was built up by using 5 independent factors, that is, diabetes mellitus, PS, hypoxemia, duration of sleep, drug resistant strain. On multivariate analysis, only the PS was significantly related to treatment incompletion in elderly patients with pulmonary tuberculosis (odds ratio: 0.41, 95% confidence interval: 0.17-0.98, p=0.04). CONCLUSIONS High PS showed a strong association with treatment incompletion in elderly patients with pulmonary tuberculosis. The PS is considered to be a useful clinical indicator.