A 44-year-old man was transferred to our department for mediastinal mass. He had suffered from only an easily fatiguable condition for 1 month. A physical examination and laboratory finding of the patient disclosed no abnormality. A chest radiograph showed a soft tissue tumor in the posterior mediastinum. It was well circumscribed and ovoid. Invasions to adjacent organs were not seen. Therefore it was though the 5th intercostal space. The tumor mass was attached to the visceral pleura of the right upper lobe by a pedicle and this pedunculated tumor laid entirely within the pleural cavity. Excision of the tumor which measured 7$ imes$7$ imes$3cm was done easily. Pathologic studies confirmed the diagnosis of localized fibrous tumor of the pleura. Localized fibrous tumor of the pleura is rare, This tumor along ith the evidence from ultrastructural and immunohistochemical studies has led most researchers to conclude that localized fibrous tumor is not of the mesothelial origin but arises in the submesothelial connective tissue.