The Southeastern Cancer Study Group has evaluated 5-fluorouracil administered intravenously weekly at a dosage of 600 mg. per M.2 as a single agent, and the 3-drug combination of cyclophosphamide doxorubicin and 5-fluorouracil in patients with metastatic carcinoma of the bladder and of the prostate previously untreated with cytotoxic chemotherapy in a prospectively randomized phase II study. In 4 of 18 patients with bladder carcinoma 5-fluorouracil induced an objective response, and cyclophosphamide, doxorubicin and 5-fluorouracil induced an objective response in 3 of 21 patients. In patients with prostatic carcinoma 5-fluorouracil induced an objective response as measured by a 50 per cent decrease in prostatic acid phosphatase determined in a central reference laboratory in 3 of 25 patients and objective stability by National Prostatic Cancer Project criteria in 14 of 29 patients. Cyclophosphamide, doxorubicin and 5-fluorouracil induced an objective response in 7 of 22 patients and objective in 20 of 29. Thus, 5-fluorouracil administered in an adequate weekly dosage is established as an effective single agent in some patients with stage D carcinoma of the bladder or prostate. However, there is no significant added benefit as measured by survival obtained for these patients by combining cyclophosphamide and doxorubicin with 5 fluorouracil.