A histopathological study was made on 53 cases of primary malignant bone tumors of the Koreans, obtained during a period of 11 years 10 months, from January 1959 to October 1970, at the Department of Pathology, National Medical Center, Seoul, Korea 1. The 53 cases of primary malignant bone tumors consist of 36 cases(67.9%) in male and 17 cases(32.1%) in female. The sex ratio of male and female was 2.1 : 1. 2. The youngest age was 2 years old and the oldest was 68 years old. 3. The 20 cases (37.8%) of 53 cases were 10∼19 years old in age group and the highest incidence, but 60∼69 years age group were only 2 cases (3.6%). 4. The 11 cases (30.6%) of 36 cases of male and 9 cases (53%) of 17 cases of female were 10∼19 years age group. 5. Osteogenic sarcoma was 21 cases (39.6%) of all malignant bone tumors. The sex ratio of male and female was 61.9% : 38.1% and the highest age incidence was 10∼19 years old group (52%). 6. Chondrosarcoma was 5 cases (9.1%) and observed in the all male. 7. Ewing’s sarcoma was 6 cases (10.7%). 8. Fibrosarcoma was 4 cases(7.2%). 9. Giant cell tumor was 2 cases (3.6%). 10. Multiple myeloma was 7 cases including 2 autopsy cases (13.2%). Male was 6 cases (85.7%), female was only 1 cases (14.3%) and its average age was 48.1 years old. 11. Malignant mesenchymal tumor was 6 cases (10.7%) 12. The most frequent site of the all malignant bone tumor was observed in femur (26.1%), in tibia (17%) and in fibula (13.2%). 13. The 53 cases of primary malignant bone tumors were histopathologically classified and tabulated.