Detailed analysis of the roentgen findings in 30 well-documented cases of parosteal osteogenic sarcoma (POS) was made. The supposedly characteristic periosteal lucency (cleavage plane) was found in only 30% of the patients. While most tumors were densely ossified, the radiodensity was uniform in only 27%. The surface of the tumor was usually irregular and a truly smooth surface was seen in only 24%. Four patients underwent arteriography; there was vessel displacement by the tumors but all were avascular. No correlation between the histologic grade of tumor and roentgen signs was found.