From April1985to March1988, 1, 005patients underwent bronchoscopic examination with chest X-ray findings suggesting possibility of tuberculosis, yet the sputum was negative for acid-fast-bacilli on repeated smear examination. In the first two years, forty-nine patients out of 660 were subsequently proven to have active disease. Among these 49 positive cases, a clinical flare-up was found in five patients with aggravated pulmonary lesions. All of these 5 aggravated lesions happened to be located in right upper lobe. In the latter one year, 345 patients underwent bronchoscopy were given postmedications with isoniazid and ofloxacine, which resulted in hardly any patient out of sixteen active cases showed aggravation of tuberculosis except one who had not taken the medicines as indicated. Our observations suggest that the exacerbation of pulmonary tuberculosis may occur with bronchoscopic examination, and the postmedication with a few supplemental drugs would be very effective to prevent these exacerbation after bronchoscopy.