A 67-year-old man was admitted to our hospital with blood sputum. Adenocarcinoma was diagnosed by sputum cytological examination. A chest X-ray film showed a tumor shadow in the lower field of the right lung. The middle and lower lobes were resected and lymph node dissection was performed. Tumor was composed of well differentiated adenocarcinoma and spindle cell sarcomatous element, and diagnosed as so-called carcinosarcoma. Pathological staging was IIIA by pT1N2M0. Postoperative chemotherapy was not performed for side effect, so radiotherapy only was done. He died of recurrence and metastasis after about 1 postoperative year.