Twenty-seven patients with a diagnosis of metastatic adenocarcinoma of the prostate were treated in a randomized, prospective trial with either Cyclophosphamide or a combination of Adriamycin, 5-Fluorouracil, and Cyclophosphamide. Doses were either Cyclophosphamide alone (800-1200 mg/m2 iv q 3 weeks) or Cyclophosphamide (150-200 mg/m2 po Day 3-6) plus 5-FU (400-500 mg/m2 iv Day 1, 8) plus Adriamycin (30-50 mg/m2 iv Day 1) given as a 4 week treatment cycle. Patients with compromised bone marrow reserve initially received the lower dose level. Objectively stable disease as defined by a modification of the National Prostatic Cancer Project criteria was seen in 53% of the 15 Cyclophosphamide treated patients and in 50% of the 12 combination treated patients. Survival was not significantly different in the two arms. However, the survival of patients responding to Cyclophosphamide was significantly longer than that of patients responding to the combination (median 18.6 months versus 8.1 months, p less than 0.05). Gastrointestinal and hematologic toxicity was moderate with both regimens. Therefore, in the present study, Cyclophosphamide alone was as effective as the combination of Cyclophosphamide, 5-FU and Adriamycin for patients with disseminated prostatic carcinoma. The moderate hematologic toxicity noted with both regimens suggests further evaluation of drug combinations utilizing higher dosages of active agents in this disease.