Anthracosis is black pigment discoloration of bronchi which can cause bronchial destruction and deformity (anthracofibrosis). A prospective, case-control study was performed to evaluate potential underlying causes of anthracosis on 190 subjects who referred for various indications. Age of patients ranged from 10-85 yrs. 46% of male patients were farmers and 27% were manual workers, whereas 91% of female patients were housewives. During bronchoscopy, special attention was given to anthracotic plaque, bronchial deformity, infiltration, or vegetation. Broncho-alveolar lavage was performed for further cytopathological, acid-fast bacilli staining (AFB) and culture in all cases. No correlation between occupational exposure to dust and two kinds of anthracosis (anthracotic plaque and antracofibrosis) was present. In anthracofibrotic patients, 81% were nonsmokers. The principal finding in bronchoscopy was simple plaque of anthracosis in 21% and anthracofibrosis in 12%. Sputum smear showed macrophages containing anthracotic granules in 71%. Patients with anthracosis had positive histopathology for tuberculosis (21%) that was not significantly different from subjects without anthracosis. Of 40 patients with simple anthracotic plaque and 22 with anthracofibrosis, only two and one patients, respectively were proven to have bronchogenic carcinoma that was not statistically more common than in the control group. Other etiology for anthracofibrosis should be investigated.