Forty-nine patients with advanced carcinoma of the breast who had received no prior chemotherapy were randomized to receive either high-dose cyclophosphamide (C) 1250 mg/M2 intravenously on day 1 and 5-fluorouracil (F) 600 mg/M2 intravenously on days 1 through 5 (CF), or vincristine (V) 1.5 mg/M2, doxorubicin (A) 50 mg/M2 and cyclophosphamide (C) 500 mg/M2 (VAC), all intravenously on day 1. Both regimens were repeated at 3-week intervals. Nine of 25 patients (36%) treated with CF and ten of 21 patients (48%) treated with VAC showed a complete or partial response as defined by the (UICC) guidelines. The estimated median time to progression for all patients was 3.5 months for CF and 6.0 months for VAC, with the median time to progression for responding patients being 8.5 months on CF and 6.3 months on VAC. Estimated survival is also similar for the two regimens. Ten of the patients treated with high-dose CF experienced septic episodes and four died. Toxicity on the CF arm necessitated premature closure of the study, and thus full statistical comparison of the efficacy of the two regimens cannot be made.