The following report is based on fifty-two cases of bone tumors classified as Ewing's tumor in the Registry of Bone Sarcoma of the American College of Surgeons,1 and two cases selected as roentgenologic and histologic types from the Massachusetts General Hospital, Boston. The number of cases in the sarcoma registry so classified is sixty-seven, or about 10 per cent, of the total registered, but some do not contain sufficient data to make a definite diagnosis, or so closely resemble other tumors, particularly osteogenic sarcomas, that they could not be included. Cases, also, in which there is too great variation in opinion have been excluded, although, in my opinion, they may belong to this group.
It must be mentioned that the data received by the registry, which usually includes the clinical history, roentgenograms and sections for microscopic study, were sent around to various pathologists and surgeons for diagnosis. This tumor