BACKGROUND: Endobronchial tuberculosis is classified into 7 subtypes as fibrostenotic type, edematous-hyperemic type, actively caseating type, tumorous type, ulcerative type, granular type and nonspecific bronchitic type by bronchoscopic features, and we make a prospective study to follow up how bronchoscopic findings change during treatment-course in each subtype of active endobronchial tuberculosis. METHODS: We planned to do follow-up bronchoscopic examination every month until there was no significant change in endobronchial lesion, then every 3 months and at the end of the treatment in each patient with biopsy proven endobronchial tuberculosis from May, 1990 to August, 1993. RESULTS: 1) This study included 66 cases, but bronchoscopic follow-up was completed as scheduled in 47 cases. 2) In actively caseating and edematous-hyperemic type, bronchostenosis occurred within 2 or 3 months of treatment in about 2/3 of total cases. 3) In fibrostenotic type, bronchostenosis did not improve in spite of the treatment. 4) In tumorous type, the changes in bronchoscopic findings were unpredictable because new lesions occured on other sites even 4 or 6 months after treatment in 2 cases and the size of initial mass increased 6 months after treatment in 1 case (among 7 cases). 5) Granular and nonspecific bronchitic type improved without significant sequelae within 2 or 3 months of treatment. CONCLUSION: It may be necessary to follow up the patient with bronchoscopy repeatedly 2 or 3 months after starting treatment in active endobronchial tuberculosis, and it is better to perform bronchoscopic examination at 6 months of treatment, especially in patients with tumorous type because there is possibility that new endobronchial lesion occurs. Aggressive therapeutic modalities such as stent-insertion, laser therapy or electrocautery should be considered to prevent bronchostenosis in cases with granulation tissue, fibrostenotic and tumorous types of endobronchial tuberculosis.