1. Primary reticulum-cell sarcoma of bone arises from the reticulo-histiocytic elements of bone marrow.

2. The authors have studied ten cases of primary reticulum-cell sarcoma of bone, and have compared the clinical, pathological and radiographic features with those of thirty-five cases of Ewing's sarcoma.

3. In their microscopic studies Hortega's staining techniques were used in addition to orthodox methods.

4. There are histological differences between a reticulum-cell sarcoma and Ewing's sarcoma.

5. Certain clinical and radiographic features help the differentiation between the two tumours.

6. The progress and treatment of the reticulum-cell sarcoma are reviewed in detail.