The purpose of this study was to introduce rotation-plasty procedure and prosthetic ambulation training. The recent development of chemotherapy and diagnostic facility have permitted the orthopaedic surgeons to try limb saving procedures rather than amputations for the treatment of the malignant bone tumors. If the tumors around the knee joint were treated by mid-thigh amputation or hip disarticulation, it would impose the client with a great handicap for rehabilitation. Rotation-plasty procedure was first done by Borggreve, in 1930 for the congenital short femur. Recently this procedure was used a malignant bone tumor at the distal femur by Kotz and Salzer in 1982. In spite of its cosmetic problem of the distal stump, this procedure has the great functional advantage of converting the above-knee amputation to the below-knee amputation. The inverted foot was also good to control the prosthesis as a below-knee stump and heel functioned as a patella to support the body weight. This 15 years old girl case was had rotation-plasty due to osteosarcoma of the distal femur with 3rd postoperative chemotherapy, and admitted to Yonsei rehabilitation hospital for prosthetic ambulation training. Then, the case had excellent functional results of prosthetic ambulation training with rotaion-plasty after 3 months.