A 63-year-old woman was referred to our hospital on June 18th, 1998 during an episode of hemoptysis that had lasted for 6 days. She had no hemorrhagic diathesis and no history of pulmonary disease. Chest X-ray films disclosed a ground-glass opacity in the right upper lung field. Bronchoscopic examination revealed bleeding from an anomalous ectopic orifice on the right lateral trachea, about 1 cm above the carina. Chest computed tomographic examinations by conventional and spiral methods readily disclosed an ectopic bronchus. Bronchial arteriography showed that the tracheal bronchus was fed by a branched vessel of the thyrocervical artery arising from the brachiocephalic artery. Atypical mycobacterium was detected in bronchoalveolar lavage fluid from the ectopic bronchus. A shunt had formed with the pulmonary artery and peripheral parts of the bronchial artery that fed the tracheal bronchus. It was speculated that the hemoptysis in this case might be due to the combined phenomena of infection and abnormal vessel formation in the tracheal bronchus. In our patient, the system of blood supply to the tracheal bronchus may have been a manifestation of atavism because it closely resembled the circulatory structure of the tracheal bronchi normally observed in sheep and giraffes. The tracheal bronchus should be taken into consideration as a potential cause of hemoptysis, inflammatory changes, and atelectasis during intubation.