The ultrasonographic appearances of osteosarcomas and the roles of ultrasonography in the diagnosis and surgical staging of osteosarcomas were investigated. A comparative study was performed on 45 cases of osteosarcomas by ultrasonography and radiography. Bony changes, periosteal reaction and soft tissue mass were evaluated for each lesion. The results showed that ultrasonography revealed a solid mass around bone in 42 patients, bone destruction in 24 patients and periosteal reaction in 16 patients. Plain radiographs showed bony changes in 44 patients and no bony change in remaining one patient, shadowing of soft tissue swelling in 30 patients, and pulmonary metastases in 3patients. Surgical biopsy and pathological examination confirmed osteosarcoma in all 45 patients.Soft tissue mass was confirmed in 42 patients surgically. The diagnostic accuracy of soft tissue masses by ultrasonography and radiography was 100 % (42/42) and 71.4 % (30/42), respectively. The positive rate of ultrasonography and radiography in displaying bony changes was 53.3 % (24/45) and 97.8 % (44/45), respectively. In conclusion, in the detection of soft tissue mass of osteosarcoma, ultrasonography is superior to radiography, and in displaying bony changes of osteosarcomas, radiography is superior to ultrasonography. So it may come to a conclusion that plain radiography combined with ultrasonography can completely display the bony and soft tissue lesion of osteosarcomas.