In a survey of 2,000 specimens of primary tumor of bone, forty-nine were found to be reticulum-cell sarcomata. The survey reinforced our conception that reticulum-cell sarcoma is a firmly established entity. It is important to establish the diagnosis by adequate biopsy. Unlike most other primary malignant conditions of bone, reticulum-cell sarcoma appears to be radiosensitive and, in one case in which the tumor disappeared, administration of Coley's toxins was the only treatment. At present, it appears that the prognosis in cases of reticulum-cell sarcoma of bone is significantly better than that in most other primary malignant tumors of bone.