Dissertation (MMED Internal Medicine)Background: Pulmonary tuberculosis smear-positive cases are expected to convert to negative sputum during treatment. Delayed sputum conversion and reversion prolong infectious period. Therefore, understanding associated factors for smear conversion and reversion will help to identify a patient with severe infectious pulmonary tuberculosis before or during treatment. Objective: The aim of this study was to determine sputum conversion and reversion rates and their associated factors among new sputum smear-positive pulmonary tuberculosis (PTB) patients. Methods: This was a prospective hospital-based study done at Iringa and Dodoma Regional Referral Hospitals. A sample size of 131 patients was recruited after being screened for AFB. The analysis was done using STATA version 12, associated factors for early sputum conversion, delayed conversion and reversion were established by univariate and multivariate logistic regression. Results: Of the 131, 98(75%) of the patients enrolled were male. Age 60+ years old aOR:0.07(95%CI:0.006-0.084) not favouring early sputum conversion, current cigarette smoking aOR: 2.892(95%CI: 0.118-0.803) was associated with delayed sputum conversions while sputum reversion was associated with current cigarette smoking a OR:3.616(95%CI:1.220-10.716). Conclusion and Recommendations: Delayed sputum conversion and reversion appear to be common among pulmonary tuberculosis. This data highlights the importance of providing smoking cessation counselling to newly diagnosed PTB patients.