Cisplatin has had only minimal activity when used as second- and third-line chemotherapy for metastatic breast cancer (MBC). There have been no phase II studies in the United States evaluating cisplatin in patients with MBC with no prior chemotherapy. We therefore treated 20 consecutive patients with cisplatin 30 mg/m2/d for four days every 3 weeks for a maximum of six courses. We obtained partial responses in nine of 19 evaluable patients (47%), with responses in liver, lung, and soft tissue indicator lesions. Our data suggest that cisplatin has substantial single-agent activity as front-line therapy in MBC, and should be considered for inclusion in first-line combination chemotherapy regimens.