Osteochondroma, the most frequent benign bone tumor, is composed of trabecular bone covered with a hyaline cartilage cap. It is well known that multiple osteochondromatosis may undergo malignant change. Such sarcomatous change usually present with the form of chondrosarcoma, and transformation to other malignancy is extremely rare. This report describes one case of osteosarcoma arising in patients who had multiple osteochondromatosis, and includes brief review of the literatures.