We performed a Phase II trial of oral leucovorin and high-dose fluorouracil (5FU) in hormone refractory patients with metastatic prostate cancer who had not had prior chemotherapy. 5FU was given as a 24-hour infusion at a dosage of 4 g/m2 and oral leucovorin at a dosage of 50 mg every 6 hours for four doses, starting with the infusion of 5FU. Fifteen patients were treated and three were not evaluable for response. There were no complete (CR) or partial responses (PR) in 12 evaluable patients (95% confidence interval for CR+PR of 0 to 26%). Three patients had stable disease and the remainder progressed. Toxicities were generally mild to moderate, but one patient died of sepsis while neutropenic. This dose and schedule of leucovorin and 5FU is not better than single-agent 5FU in patients with metastatic prostate cancer.