BACKGROUND: The length of postoperative drug therapy remains controversial in pulmonary tuberculosis. We analyzed our experiences to determine the postoperative duration of chemotherapy after resection. METHODS: A retrospective review was performed in 66 of 95 patients that underwent pulmonary resection for pulmonary tuberculosis between January 1993 and December 1998. We compared the relapse rates according to the length of postoperative chemotherapy in each group, classified by the results of sputum AFB culture before the surgery, the number of resistant durgs, the number of prior treatment and the division of anti-TB drugs used postoperatively. RESULTS: Fifty three of 66(80.3%) were men and 13(19.7%) were women with a median age of 33.5 years(range, 16 to 63). The mean lengths of the pre-and post-operative chemotherapies were 4.9 months, and 12.9 months respectively. Five of 66 patients(7.6%) relapsed during the mean period of follow up(39.7 months). In the group less than three times of the prior treatment, there were two relapses(20%) in Ed-the highlight above-rephrase 10 patients that were medicated for 6 months or less, and one relapse in 43 patients(2.3%) that took medicine for more than 6 months(p=0.03). In the group using second-line drugs postoperatively, there was one relapse(25%) in four patients that were medicated for 12 months or less. No patient in a total of 17 that received medicine for more than 12 months relapsed(p=0.03). CONCLUSION: We recommend that patients with the prior treatment less than three times should be treated for more than 6 months after resection and patients using the second-line drugs postoperatively should be medicated for more than 12 months.