The treatment of multi-drug resistant tuberculosis (MDR-TB) is complicated and results are not always satisfactory. We aimed to investigate treatment results of our patients, relapse rates, factors affecting treatment outcome. We evaluated prospectively, 142 patients, who had been hospitalised with diagnosis of MDR-TB in our clinic between January 1995-December 2000 at Sureyyapasa Chest Diseases and Chest Surgery Training and Research Hospital in Istanbul, Turkey. All patients were male and human immunodeficiency virus negative. The mean age was 39 + or - 11 (16-65) years. A mean number of 5.5 + or - 0.8 (4-8) second line drugs, including one parenteral drug, were administered. Of 142 patients, 102 (71.8%) were classified as cured, 16 (11.3%) patients were defaulters, failure was seen in 10 (7.0%) patients and 14 (9.9%) patients died during treatment. Surgical resection was applied in 35 patients and cure was achieved in 88.5% of them. Of 102 patients who were cured, 89 (87.2%) were available for follow up and mean duration of follow up was 19.2 + or - 10.3 (12-72) months. Relapse was not detected in any of them. Patients with unsuccessful outcomes had a higher incidence and higher mean number of second-line drugs usage in previous regimens, higher incidence of antecedent prothionamide and ofloxacin usage, higher incidence of extensive radiologic involvement and withdrawal of responsible drugs due to adverse effects. Limited radiologic involvement, non-usage of antecedent prothionamide and adjuvant surgery were found as significant independent factors effecting successful treatment outcome. MDR-TB is a complex but a treatable disease. To know much more about the factors effecting treatment results and to arrange the proper conditions, are expected to make increases in the success rates of MDR-TB treatment.