We successfully treated surgically using cardiopulmonary bypass an elderly patient, a seventy-six-year-old man, with primary advanced lung cancer (rt. S6) with left atrial extension. He had intermittent episodes of bloody sputum. A preoperative chest roentogenogram revealed an abnormal mass shadow in S6 of the right lower lobe of the lung. MRI findings of the chest and a right heart catheterization with levophase demonstrated the extension of the tumor into the left atrium. A distant metastatic work-up was negative. By use of the full lateral thoracotomy and cardiopulmonary bypass, the tumor was removed en bloc through a combined left atrial resection and right middle and lower lobectomy. The patient has been well without and symptoms 8 months after surgery. An advanced lung cancer invading the left atrium can be safety and completely resected with the use of cardiopulmonary bypass if the extent of left atrial involvement is recognized preoperatively.