Seventy-seven patients with metastatic transitional cell carcinoma of the bladder who were unable to receive primary Cisplatin-based therapy or failed primary chemotherapy received one of three sequential 5-Fluorouracil-based salvage regimens: a) 5-Fluorouracil (1000 mg/m2 B.S.A. x 5 days) and Mitomycin-C (14 mg/m2 B.S.A. 6 week intervals), b) 5-Fluorouracil (750 mg/m2 B.S.A. x 5 days) and a-Interferon (5 miu/m2 B.S.A. daily x 5 then 3 times a week (TIW), c) 5-Fluorouracil (500 mg/m2 B.S.A. x 5 days), a-Interferon (5 miu/m2 B.S.A. x 5 days then TIW) and 13-Cis Retinoic Acid in escalating doses daily. Only 1 (6%) of the patients with regimen A responded, whereas 9 (30%) of the patients with regimen B and 8 (27%) in regimen C responded. Although all responses were partial remissions, responses were seen in patients with advanced and initially refractory transitional cell carcinomas. This data reveals that a-Interferon and 5-Fluorouracil is an effective combination in the treatment of metastatic transitional cell carcinoma and worthy of further study.