Twenty-six cycles of high-dose ifosfamide + mesna (HD-IFO + M) were applied to seven female patients with advanced breast cancer refractory to prior treatment, using three different durations of continuous infusion (4, 24, and 48 h) every 3 weeks. To evaluate the most tolerable time schedule, the duration of the infusions was changed periodically in each patient. Toxicity was low in general, but continuous infusion of HD-IFO + M over 24 h appeared to be the best tolerated. One partial response lasting 27 weeks was achieved and four patients achieved stable disease lasting from 9 to 12 weeks.