1.1.Background:Failure of anti tuberculosis treatment can lead to some serious and unwanted consequences. This study aimed to determine the prevalence of treatment failure among patients diagnosed with pulmonary tuberculosis at Mufti Mahmood Memorial Teaching Hospital Dera Ismail Khan Pakistan. 1.2.Materials and methods:Consecutive patients of smear positive PTB, managed between February 2011 to October 2013 at the directly observed therapy (Tuberculosis) unit of Mufti Mahmood Memorial Teaching Hospital Dera Ismail Khan Pakistan were enrolled for the study. Each patient was required to have a sputum specimen collected and examined for the presence of acid fast bacilli (AFB). This was done at the time of enrolment into the study and at the end of 2nd (in category I cases only), 3rd (in category II cases only) and at the end 5th and 7th month of anti-tuberculosis treatment. 1.3.Results:144 patients were recruited and 20 were lost to follow up or had transferred out. 124 patients consisting of 53 (42.74%) males and 71 (57.26%) females aged 14-85 years completed the study. Ninety three (75%) of the patients were New (category I) at the time of enrolment while 31 (25%) were Retreatment cases (category II). Among 124 smear positive patients at baseline, 22 (17.74%) out of 93 were sputum smear positive at the end of 2nd month, 2 (2.15%) patients at were sputum smear positive at the end of 5th and 7th month respectively in category-1 patients, and 10 (32.26%) out of 31 patients from category 2 had been sputum positive at the end of3rd month of treatment and 4 (12.90%) patients remained positive at the end of 5th and 7th month of treatment respectively. 1.4.Conclusion:Prevalence of treatment failure was significant in our study (4.84%) and it demonstrated a requirement of vigilance on part of health personnel because drug resistant tuberculosis, if untreated, poses a threat to all contacts of patients with tuberculosis.