Clear cell tumor of the lung is a rare benign tumor. We report herein a case of clear cell tumor of the lung. A 45 year-old woman with a round mass lesion of approximately 2 cm diameter on chest X-ray underwent a thoracotomy. Pathologic examination revealed sheets of large round or polygonal cells with clear cytoplasm and immunoreactive positivity for HMB-45 and vimentin. Investigation with abdominal CT scans showed no evidence of renal disease, and the tumor was diagnosed as clear cell tumor of the lung. © 2006 The Japan Society of Clinical Oncology.