1. Skeletal involvement occurs in less than one per cent. of cases of hydatid disease.
2. A roentgenographic diagnosis of osseous hydatid disease is extremely difficult.
3. But three cases of osseous hydatid have been reported in this country up to 1930.
4. Two additional cases (in both of which the bones of the pelvic girdle were involved) are reported from the Bone Tumor Department of the Memorial Hospital.
5. Intensive radiation therapy failed to check the disease or to alleviate the symptoms in our cases.
6. Hydatid disease should be considered among the causes of unusual bone tumors, from several types of which it is not always easily distinguishable.