In recent years, significant progress has been made in the treatment of primary malignant bone tumors. The surgeon is confronted with increasing demand for limb-sparing surgery by patients and parents alike. In the skeletally immature, resection of the growing physis will ultimately result in leg length discrepancies and functional impairment. An adequate reconstruction therefore calls for the compensation of the expected growth deficit to achieve symmetry and an optimized function of the extremity. Between 1975 and 2000, 55 patients (24 female, 31 male) were referred and treated at our institution. All patients were not older than 10 years (4.2-10, mean: 7.9 years). Histological diagnosis was Ewing's tumors ( n=19) and osteosarcoma ( n=36). Localization in the extremities was predominantly in the lower extremity with 63.6% around the knee joint (distal femur and proximal tibia). Surgical treatment was performed in all patients. Endoprosthetic reconstruction was performed in 34 patients (lower extremity n=30, 29 Howmedica Modular Reconstruction System, HMRS, 1 Pafford prosthesis; upper extremity n=4, 4 HMRS); in another case of humeral tumor involvement a resection replantation procedure was carried out. The other patients received a rotationplasty ( n=7), a biologic reconstruction ( n=6), resection replantation of the humerus ( n=1), no reconstruction ( n=3), or had to be amputated ( n=4). After a mean follow-up of 114 months (24-256 months) 11 patients had died. Even in young children endoprosthetic reconstruction with relatively early mobilization and high quality of life can be a very successful method for limb salvage. Optimal reconstructive results following resection of primary malignant bone tumors in children are reached when indications and limitations of each method are carefully considered on an individual basis taking into account the patients' expectations.