This report describes the unusually high response rate of metastatic synovial sarcoma to high dose ifosfamide (14-18 g/m2) when that drug was used to treat 13 consecutive patients with recurrent metastatic synovial sarcoma before surgery (or thoracotomies) to provide optimal salvage therapy for these patients. Thirteen patients with recurrent or pulmonary metastatic synovial sarcoma seen at the Cedars-Sinai Comprehensive Cancer Center (Los Angeles, CA) from April, 1989 through January, 1993 were treated with high dose ifosfamide (14-18 g/m2). Ifosfamide was infused at the dose of 2 g/m2 over a 4-hour bolus infusion, followed by 2-g/m2 24-hour continuous infusions of ifosfamide, for a total of 14 or 18 g/m2 (6-8 days). Mesna (Mesnex, Bristol-Myers Oncology, Princeton, NJ) was infused with the ifosfamide at equimolar doses. Supplemental sodium bicarbonate (180 mEq) was given daily to prevent severe acidosis. Nine of the thirteen patients were treated with prior chemotherapy for their primary tumors. Prior chemotherapy consisted of doxorubicin (Adriamycin, Adria Labs, Dublin, OH) in all patients and doxorubicin combined with cisplatin in eight of them. All 13 patients had objective responses to high dose ifosfamide chemotherapy. There were nine partial responses and four complete responses. Five of the patients died of disease at 20-40 months (median, 27 months) from initial therapy. Eight patients have survived from 2 to 43 months (median, 20 months) from initial therapy, and three of these patients are disease free. Those patients surviving disease free had successful surgical removal of their residual metastatic disease after chemotherapy. Metastatic synovial sarcoma appears to be particularly sensitive to high dose ifosfamide chemotherapy. This experience suggests that there is a role for high dose ifosfamide chemotherapy in preoperative and postoperative adjuvant chemotherapy for primary synovial sarcoma, which is usually always a high grade malignant lesion with a poor prognosis after surgery alone.