A 71-year-old woman underwent radical resection in May 1994 for a mediastinal mass invading the anterior chest wall. Histopathological examination revealed adenosquamous cell carcinoma. She was treated with postoperative chemotherapy including 5-fluorouracil (5-FU) and 4'-D-tetrahydropyrayl-doxorubicin (THP), based on in vitro chemosensitivity testing (CST), by MTT assay, using a surgical specimen. In December 1994, a recurrent tumor was detected on the left anterior chest wall and the patient received two courses of 5-FU, THP and methotrexate (MTX). The size of the chest-wall tumor decreased 25%. In July 1995, the patient had involvement of the left axillary lymph node and brain metastases in addition to the mass on the chest wall. Therefore, cisplatin, 5-FU and MTX were selected as treatment agents, based on CST using a metastatic axillary lymph node. After two courses of these agents, chest computed tomography showed a 91% reduction in the size of the chest wall tumor. Radiation was administered for the brain metastasis. In March 1997, the patient died of thymic carcinoma.