Intralobar pulmonary sequestration is a rare congenital malformation characterized by a cystic portion of the lung that derives its arterial blood supply through aberrant vessel directly of systemic circulation. Intralobar pulmonary sequestration Is usually contained within the visceral pleura of a pulmonary lobe and its venous drainage to the pulmonary venous system. We experienced a case of pulmonary sequestration preoperatively confirmed. The patient was 17 year old female whose complaints were mild fever and profuse purulent sputum. Chest film showed a large thin walled cystic lesion with air-fluid level at the left lower posterior basal lung field. Aortogram revealed an aberrant artery originated from thoracic aorta just above the diaphragm and that drained via pulmonary vein into the left atrium. At time of operation, a large abscess cavity measuring 9x8x3 cm in dimension at the left lower lobe was noted. And the aberrant artery, measuring 0.5 cm in diameter and 2 cm in length, arising from thoracic aorta just above the diaphragm was noted. After division and ligation of the aberrant artery, a left lower lobectomy was performed and the patient`s postoperative course was uneventful.[KTCS 1981;4:354-358]