A case of a 60-year-old man who had a chronic expanding hematoma with an intrapulmonary fresh hemorrhage in the right thorax is reported. He suffered blunt trauma of his right thorax in a traffic accident 25 years ago. He has no symptoms and signs after the accident. But he had hemoptysis twice and he was taken to our hospital. He underwent the resection of the chronic expanding hematoma and right lower lobe of the lung. The surgical specimen consisted of the hematoma measuring 17 x 13 x 6 cm. The chronic expanding hematoma contained aseptic brownish muddy substances. The patient recovered without complications and hemoptysis. Chronic expanding hematomas occur in many locations, often simulating neoplasms. Although the mechanism of chronic expanding hematoma is unclear, the self-perpetuating expanding nature of the lesion may appear to be due to the irritant effects of blood and its breakdown products, causing repeated exudation or bleeding from capillaries in the granulation tissue.