Forty-four women with advanced breast cancer participated in a prospective clinical trial to evaluate the efficacy and toxicity of a regimen consisting of cytosine arabinoside and cisplatin. All patients had previously received chemotherapy. Three patients (7%) responded to therapy with response durations of 153, 160, and 441 days. The median time to disease progression and median survival time in all 44 patients were 2.3 and 5 months, respectively. This regimen had significant toxicity, with most patients experiencing severe or life-threatening hematologic, renal, or infectious complications. This regimen cannot be recommended for previously treated patients with advanced breast cancer.