High-dose ifosfamide (HD-IFX) has shown significant antitumor activity in advanced sarcoma and breast carcinoma. The use of uroprotective agents and the availability of ambulatory continuous-infusion pumps has allowed dose escalation in the administration of ifosfamide (IFX) on an outpatient schedule. We report the results of a phase II trial of IFX given at high doses to heavily pretreated patients. IFX was infused at 2 g/m2 per day for a total of 7 days through a central venous access, with cycles being repeated every 21 days. Mesna was given concomitantly at equimolar doses. No hematopoietic support was used. A total of 27 heavily pretreated patients whose disease had progressed during conventional-dose chemotherapy were included (14 sarcomas, 10 breast carcinomas, and 3 bladder carcinomas). Reversible neutropenia and gastrointestinal toxicity were the most frequently encountered toxicities. Only two patients developed transient renal failure, and two others developed central nervous system toxicity. No treatment-related death was observed. Of 22 patients who were evaluable for response, 6 (27%) showed an objective response (OR), all ORs being partial responses (PRs) with a median duration of 6 months, and 12 patients had stable disease (SD; 55%) with a median duration of 3.5 months. The median overall survival (OS) was 6 months. Three patients underwent high-dose chemotherapy after showing a response to our IFX schedule. We conclude that continuous-infusion IFX given in an outpatient setting is a feasible and active regimen that produces, a manageable toxicity profile in heavily pretreated breast cancer and sarcoma patients. Early institution of this schedule in less advanced stages could improve the results obtained.