AbstractCyclophosphamide has been considered one of the reference drugs of chemotherapy in randomized trials in hormone-refractory prostate cancer by the National Prostatic Cancer Project (NPCP). Ifosfamide, another oxazaphosphorine agent, and an analog of cyclophosphamide, appears to be more active and less toxic in a broad spectrum of tumors. Fifteen patients with metastatic hormone-refractory prostate cancer were treated with continuous infusion of ifosfamide 2 g/m2per day for 2 days, together with the uroepithelial protective agent Mesna 2.4 g/m2per day for 2 days, both to be repeated every 3 weeks. All patients have failed on previous hormonal therapy and 7 patients had received previous chemotherapy. The median age was 66 years. Fourteen patients were evaluable; none of whom achieved an objective response. Four patients were stabilized and 10 had disease progression while on chemotherapy. Major toxicity included 2 reversible encephalopathy, 3 grade I reversible renal toxicity, and 1 hemorrhagic cystitis. We concluded that ifosfamide given in this schedule in this group of patients is not an active agent in prostate cancer.