In spite of existence of effective chemotherapy for treating tuberculosis for more than five decades, tuberculosis remains a major public health problem. The most important cause of tuberculosis treatment failure among detected patients is non-completion of treatment, or default.The goal is to determine percentage of defaulters in one of the Egyptian chest hospitals in a retrospective study of tuberculous cases attended during the last ten years. A defaulter is defined as a patient who interrupted treatment for two consecutive months or more before the end of the course of treatment.Data about cases was collected from their treatment files in the hospital, statistics of defaulters are done in a trial to detect causes, risk factors or associations with treatment defaulting in order to decrease this percentage in the future treatment programs.10.5% was the percentage of defaulter during the last ten years. However, males, geriatric age group, cases having relapse of pulmonary tuberculosis, cases with smear-ve pulmonary tuberculosis and those who received treatment with regimen II have higher percentage.Patients with a history of treatment default are more liable to default again. There is a clear need to specify certain (risky) groups for defaulting and to apply additional measures to prevent them from defaulting.