We studied recurrence patterns in 255 patients with high-grade osteosarcoma of the extremity and the efficacy of the treatment of these recurrences. One hundred seven patients developed metastatic disease: 77 had isolated pulmonary metastases, 17 had simultaneous metastases to lung and elsewhere, and 13 had metastases to other sites. Of the 77 patients with metastases confined to the lung, 51 (66%) underwent thoracotomy for resection of the metastases, and 13 (17%) are long-term disease-free survivors. Patients with simultaneous metastases to lung and other sites, and patients with metastases to sites other than lung, have a poor prognosis with only one long-term disease-free survivor in these groups. Thoracotomy has a limited role in the treatment of metastatic disease. Improvements in aggressive, systemic chemotherapy are essential for improving the prognosis in these patients.