A study of 102 osteogenic sarcomas of the bone surface revealed that 79 were parosteal osteogenic sarcomas. Roentgenographically, these 79 were dense, lobulated lesions attached by a broad base to underlying bone, usually the lower femoral shaft. Histologically, they were low-grade osteosarcomas. The other 23 lesions (periosteal osteogenic sarcoma) usually involved the upper tibial shaft and presented as small radiolucent lesions on the surface, with formation of spicules of bone perpendicular to the bone shaft. Histologically, these 23 were relatively high-grade, predominantly chondroblastic osteogenic sarcomas. Thirteen of the 23 patients were males, and most were in the second decade of life. Of five patients who had excision of the tumor, two had recurrence. Seven of 13 patients who underwent amputation initially were alive without disease at last follow-up. Only 4 of the 23 patients have dies of metastatic disease.