There is no evidence that combination chemotherapy is superior to single agents in the treatment of advanced, hormone-resistant carcinoma of the prostate. We are reporting the preliminary results of a randomized trial comparing cyclophosphamide (CTX) with a combination of 5-fluorouracil, doxorubicin and mitomycin C (FAM'). Thirty-one patients were randomized and 30 of them were evaluable for response. Sixteen patients were treated with CTX and 14 with FAM'. On the CTX arm, eight (50%) of the patients had stable disease (SD) and eight (50%) had progressive disease (PD). On the FAM' arm, one (7%) patient had partial response (PR), five (36%) patients had SD and eight (57%) failed to respond. The difference in response rates between the two regimens was not significant (P greater than .72). The median time to progression (MTP) of all patients treated with CTX was six weeks and the MTP of patients treated with FAM' was 16 weeks (P less than .007). This difference in MTP could be explained in part by the unequal time to reevaluation between the two regimens. The MTP of the responders on CTX however, was 13 weeks, while for FAM' it was 33 weeks (P = .014). This difference suggests that FAM' has superior activity to CTX. Pain alleviation was seen in 25% of patients treated with CTX and in 64% of those treated with FAM' (P less than .01). Toxicity was tolerable on both regimens. We conclude that CTX and FAM' have similar response rates. Patients treated with FAM' enjoyed longer MTP and greater pain alleviation than those treated with CTX.