We report on the clinical course and outcome of 28 patients, treated at The Istituti Ortopedici Rizzoli between 1995 and 1997 for osteosarcoma of the extremities metastatic to the lung at presentation. The treatment for these patients was the following: primary chemotherapy with cisplatin, adriamycin and high dose of methotrexate and ifosfamide followed by simultaneous resection of primary and metastatic lesions (when feasible), and further chemotherapy. After primary chemotherapy, lung metastases disappeared in 6 patients, whereas metastases in 3 remained surgically unresectable. These 9 patients received surgical treatment of the primary tumor only. In the remaining 19 patients, after chemotherapy, a simultaneous resection of the primary and metastatic tumor was performed. The resection of metastatic lesions was complete in 18 cases and incomplete in one. Three of the 4 patients who did not achieve a tumor-free status died in a few months and one is still alive with uncontrolled disease. With a median follow-up of 32 months (19-43) of the 24 patients who achieved remission, 12 (55%) remained continuously free of disease, 11 relapsed with new metastases and 1 died of chemotherapy-related toxicity. The 2-year DFS and OS were 36% and 53% respectively. These results are much worse than those achieved in 114 contemporary patients with localised disease (2-year DFS: 81%) treated in the same period and they are superimposible to the results achieved in 23 patients previously treated with the same protocol, but with standard dose of ifosfamide (2-year DFS: 32%). However, it must be underlined that, as regards prognosis, patients with metastatic disease at presentation are a hetero-geneous group. The DFS was significantly higher for patients with only one or two metastatic lesions than for patients with 3 or more lesions (2 year DFS: 78% vs. 28%). In 12 of the 19 patients who had a complete simultaneous resection of the primary and metastatic tumor, a strong correlation between the degree of necrosis of the primary and metastatic lesions was found. We conclude that in patients with osteosarcoma of the extremity with lung metastases at presentation: a) the combination of aggressive chemotherapy with simultaneous resection of primary and metastatic tumors works very well only for those patients who present with one or two metastatic nodules whereas for patients with 3 or more pulmonary metastases the prognosis is very poor; b) within the 4-drug regimen used in this study, the increment of ifosfamide dose from 10 g/m2 to 15 g/m2 for cycle does not improve prognosis; c) the strong correlation found between the histologic response of the primary tumor and metastases supports the strategy, largely used nowadays in the neoadjuvant treatment of osteosarcoma, of tailoring postoperative chemo-therapy on the basis of the primary tumor histologic response to preoperative chemotherapy.