A series of clinical and pathological studies were performed on 74 cartilaginous bone tumors including osteochondromas, multiple cartilaginous exostoses, chondromas, chondromatoses, benign chondroblastomas and chondrosarcomas. Resection was adequate for the osteochondromas, and no recurrence was observed. Out of 14 multiple cartilaginous exostoses, three, all in flat bones showed malignant change. The predominant sites of chondroma were the finger and toe bones, and curettage and bone graft was adequate treatment. Neither recurrence nor malignant change was observed. Two cases of chondromatosis, one of Ollier's disease and one of Maffucci's syndrome, were included in our series. Leg length discrepancy and pathologic fracture were common problems in chondromatosis. Moreover, malignant change was suspected in a hemangioma of the Maffucci's syndrome patient. Benign chondroblastoma was treated by curettage and bone graft, with no recurrence. In our series, 4 primary and 3 secondary chondrosarcomas were observed. Metastasis was seen in only one case. Because of the discrepancy between the biological behavior and histological findings of cartilaginous bone tumors, the malignancy of tumors should be evaluated by clinical signs and symptoms as well as by histological findings.