Gemcitabine is an antimetabolite drug with proven antitumor activity and tolerability in metastatic breast cancer. In a total of nine studies, gemcitabine monotherapy has reached response rates of up to 37% in the first-line setting, 26% in the second-line setting, and 18% or better in the third-line setting. Gemcitabine is an excellent choice for combination therapy by its unique mechanism of action and favorable toxicity profile, thus limiting the risk of pretreatment-related drug resistance and overlapping toxicity, and by its potential for synergistic interaction with some combination partners as indicated in preclinical studies. Numerous phase II clinical studies have combined gemcitabine with other active agents such as the taxanes, vinorelbine, vindesine, cisplatin, 5-fluoro-uracil, as well as anthracyclines across various regimens and conditions of pretreatment. Most of these two-drug combinations have consistently demonstrated higher efficacy than either single agent, particularly in pretreated patients. Even higher efficacy has been obtained with triple-drug regimens including gemcitabine, anthracyclines (epirubicin or doxorubicin), and paclitaxel; these regimens have yielded overall response rates of 58-92% as first-line treatment. In view of these results, gemcitabine may be regarded as a valuable alternative to the palliative treatment of metastatic breast cancer, and an excellent option for the development of effective combination treatment not only in first-line therapy, but also for intensively pretreated patients previously exposed to anthracyclines and/or the taxanes. Copyright (C) 2003 S. Karger AG, Basel.