Lonidamine (LND) is a unique antineoplastic drug derived from indazole-3-carboxylic acid which inhibits oxygen consumption and aerobic glycolysis, interfering with energy metabolism of neoplastic cells. LND has been experimentally shown to potentiate the cytotoxic effects of epirubicin (EPI) in human breast cancer cell lines, cisplatin activity in both platinum-sensitive and -resistant human ovarian carcinoma cell lines, and EPI antineoplastic activity in some recent phase III trials carried out in advanced breast cancer. A multicenter phase II trial was carried out with the combination of cisplatin 60 mg/m2, EPI 100 mg/m2 and LND 450 mg/day p.o. in three refracted doses/day starting 2 days before cisplatin and EPI (day -2 and -1), stopping 2 days after chemotherapy (day 0, +1 and +2). Thirty patients with metastatic breast cancer were enrolled into the study. Twenty-nine patients were evaluable for objective response. The overall response rate accordingly to an intent-to-treat analysis was 73% (95% CL 54-88%). Four patients achieved complete response (13%; 95% CL 4-31%) with a median duration of 9.5 months (range 4-16) and 18 patients had partial response (60%; 95% CL 41-77%) with a median duration of 9.8 months. Stable disease was obtained in five cases (17%) and progressive disease was recorded in three patients. One patient died of progressive cancer before restaging. The overall median survival of the whole series of patients was 14+ months. The most frequent toxicities were represented by gastrointestinal and hematological side effects. The combination of cisplatin + EPI plus oral LND is active against metastatic breast carcinoma. The antineoplastic activity of the cisplatin + EPI + LND regimen is as high as that reported for more aggressive regimens such as the fluorouracil + doxorubicin + cyclophosphamide combinations without an increase in toxic effects.