OBJECTIVES: This study was designed to evaluate treatment outcome of pulmonary tuberculosis patients by using WHO/IUATLD classification and investigate factors associated with unsuccessful outcome. METHODS: The study was designed as a retrospective evaluation of patients with smear confirmed pulmonary tuberculosis visiting two specialized hospitals in North East Libya. All patients who registered during 2008-2009 were enrolled. Standardized protocol was used to collect the required data. Descriptive analysis was computed for demographic and clinical characteristics. Chi-square test with significance level of 0.05 was used to determine association between variables. Data was analyzed by Statistical Package for the Social Sciences version 16.02. RESULTS: Three hundred and twenty seven patients were notified during the study period. Using the WHO/IUATLD criteria, cure and treatment completion rate was 1.2% and 57.5%, respectively. Treatment failure occurred in 7(2.1%) cases.  Ninety (27.5%) patients defaulted treatment, 11 (3.4%) died and 26 (8%) transferred out. Nationality, sex, educational level, area of residence and smoking were associated with unsuccessful treatment outcome. CONCLUSIONS: Improving clinical and laboratory infrastructure in peripheral areas, educating defaulters about benefits of completing therapy and stratifying foreigners as high risk groups could improve success rate.   Measures should be taken to improve professional commitment and expertise of health care professionals