Thirty-eight patients presented with previously untreated, predominantly low-grade juxtacortical osteosarcoma. There were 12 (32%) men and 26 (68%) women with a mean age of 28.9 years. The most common sites of tumor were the distal femur (n = 28) and proximal tibia (n = 5). Twenty-five patients presented with Stage IB tumors. Twelve had Stage IIB, which although it was predominantly low-grade, had an area of high grade tumor, so the tumors were considered dedifferentiated. One patient had Stage III tumor. All patients were alive at 6.75 years' average followup. Negative but close margins were achieved in all but two patients (range, 1-80 mm). Intramedullary extension was seen in 17 (44.7%) patients, and the adjacent cortex was involved in 27 (71.1%) patients. There was no statistically significant difference between tumor size, site, radiographic appearance, cortical or intramedullary extension, grade, resection margin, or pretreatment duration of symptoms and local recurrence. Intramedullary extension of tumor does not seem to increase the risk of metastatic disease. Dedifferentiation of predominantly low-grade juxtacortical osteosarcoma in not previously treated tumors is uncommon. Based on these data, close but negative margins may be adequate in achieving local disease control and preventing metastases in these patients.