The purpose of this study is to introduce prosthetic discipline and ambulation training after hemipelvectomy due to osteosarcoma. Over the past years, when the malignant bone tumors occurs in the extremities amputation is not enough to prevent a part recurrence and distal transformation resulting in fatal prognosis. On the other hand, these procedures could bring about a difficulty in rehabilitation in curing patient who have had hemipelvectomy. However the recent development of chemotherapy and diagnostic facility have permitted the orthopedic surgeons to many try amputations for the treatment of the malignant bone tumors. Unfortunately, there has not been many researches on hemipelvectomy. Since there is no studies found on hemipelvectomy either. Therefore, we introduce successful procedures for rehabilitation through the ambulation training for patients who have had amputation. One of our patients, who is an eighteen years old male, has had hemipelvectomy on the eighteenth of June in 1997 after his anticancer treatment over 12 times. He has had physical therapy of prosthetic ambulation training at the department of rehabilitation medicine Yonsei University Medical Center from the fifteenth of October to December '2nd in 1997.