OSTEOGENIC sarcoma may be defined as a primary malignant tumor derived from tissues which normally produce bone. Naturally most of these arise in bone, but recent reports (1) in the literature indicate that bone-forming malignant tumors have been observed in the thyroid gland and other organs not associated with bone. If it is true that any primary bone tumor may be regarded as a potential malignancy (2), and if, in spite of all known therapy, the disease carries an unusually high mortality rate, it is obvious that most earnest consideration of this rare disease is justifiable. From the reports in the literature, one is impressed with the comparatively small number of primary bone malignancies encountered, even in the large clinics. Doubtless, there are many in this assembly whose experience with this rare disease far exceeds that of the writer, and it is not presumed that any new development will be presented. The purpose of this paper is, then, to record a limited experience, and to reiterate some of the well-known facts and thereby, if possible, to encourage further interest in this sector of malignant disease. The great volume of literature written in recent years would seem to indicate a revival of interest in this subject. This has doubtless been stimulated by the establishment of the Bone Sarcoma Registry by the American College of Surgeons. The good work which this organization is doing is to be commended, and it is hoped that through this or some such means there may be established a more hearty co-operation of all practitioners who deal with this condition. It is hoped to develop thereby a greater diagnostic accuracy and a more effective therapeusis. The first thought in connection with malignancy is the conservation of life, and in osteogenic sarcoma the conservation of limb also, since the majority of these tumors occur in the long bones of the extremities. In 17 years there have been 210 primary tumors of bone recorded in the Scott and White Clinic from a total of 144,889 clinic registrations, or approximately one in 690 admissions. Of these 210, there are 35 which have been classified as malignant, through the criteria of history, physical examination, and roentgenologic study. In addition, 23 of the 35 have had biposy, post-operative, or postmortem pathologic examinations. Thus it will be seen that in this institution one primary malignant bone disease has been encountered in approximately 4,000 clinic admissions. Roentgenology has contributed to a better understanding of this condition, because it offers a superior method of skeletal examination, but it is to be remembered that there are yet some unsettled problems in. relation to classification. Some of the earlier writings, after the advent of roentgenology, would indicate that the lines of distinction were sharply drawn between the benign and malignant groups, and that the further subdivision of these two classes might be comparatively easy.