A combination of platinum (100 mg/m2 in a 24-h continuous i.v. infusion) and mitomycin C (10 mg/m2 i.v. push at the end of the cisplatin infusion) was administered in 20 patients with advanced breast cancer refractory to conventional treatments (CMF and anthracycline-containing regimens, hormonal therapies). The response rate was 20% (4/20), including one complete response of lung metastases which lasted 12 months. Median duration of partial responses was 4 months. Major toxicity was gastrointestinal and it was superimposable to that observed with other cisplatin-containing regimens. A marked and prolonged asthenia was reported in 6/20 patients (30%), and the regimen's compliance was poor. We conclude that at these doses and schedule, the cisplatin and mitomycin C combination has a limited efficacy in advanced breast cancer patients, and its use is not recommended in pretreated patients.