Primary malignant, benign bone tumor, and tumorlike lesions are not rare in orthopedic field, and well known for it's high recurrence and mortality. The conventional methods of treatment are radical surgery, anticancer chemotherapy, and radiation therapy for malignant bone tumor. curettage and bone graft, en bloc resection, and prosthetic replacement for benign bone tumor and tumorlike lesions. Methylmethacrylate has been used adjunctively in the treatment of bone tumor which was difficult or impossible by above methods. We had treated 53 cases of malignant and benign bone tumors by using methylmethacrylate bone cement and reviewed the results during a period of 10 years from January, 1981 to January, 1990. The results were as follows. l. Among the 53 cases, the metastatic bone tumor which was pathologically fractured were 24 cases, giant cell tumor 14 cases, osteosarcoma 7 cases, parosteal sarcoma and chondrosarcoma 2 respectively, simple bone cyst 2 cases, and osteoblastoma, chondroblastoma 1 case, respectively. 2. The operative procedure was performed by filling the dead space with bone cement without bone graft after thorough curettage for benign tumors and bone cement was used adjunctively with metalic internal fixation and tumor prosthesis for primary malignant tumors and pathologic fractures. 3. The complications were wound infection, joint stiffness near the lesion, local recurrence, and death which was asociated with disease. 4. The methylmethacrylate bone coment may be used for space filler of bony defect, rigid internal fixator and sometimes as local cytotoxic agent by the heat generation during the process of polymerization.