The origin of hamartoma from the Greek words for "error" and "tumor" is credited to Albrecht who in 1904 described a disorganized arrangement of tissues normally present in an organ and applied also to tumors found in many organs other than the lung. The hamartoma is the most common benign tumor of the lung and revealed accidentally as asymptomatic coin lesion on routine chest X-ray, but the incidence is very low and especially endobronchial origin extremely low. We have been successful surgical experienced one case of a 36-year-old female having endobronchial hamartoma, 4x2.Sx2 cm in size and located at right main bronchial lumen near the carina, which consists of a hard, nodular surfaced mass and adhered to the cartilaginous portion of the right upper lobe bronchus by dense fibrous band and migrate to trachea on expiration or coughing. This case was not suspected by chest X-ray or bronchogram and confirmed bronchoscopy with biopsy. Right pneumonectomy was inevitable because of bronchiectatic change of right bronchus due to tumor obstruction. She was discharged with relatively good general condition on 21 days postoperatively.[KTCS 1983;1:161-166]KTCS 1983;1:161-166]