Based on the synergistic interactions of the sequence doxorubicin-paclitaxel-gemcitabine obtained in our preclinical study, a Phase I trial was conducted to evaluate the feasibility of this new sequence in breast cancer. Patients with stage IIIB-IV breast cancer received doxorubicin on day 1, paclitaxel on day 2 and gemcitabine on day 6 and 13 (steps IIa, III and V) in cohorts of 3 patients. From March 1999 to December 2000, 9 patients were treated. The most important toxicity was hematological. The maximum tolerated dose was reached at the second level because dose-limiting toxicity occurred in 3 patients. Non hematological toxicities were alopecia, diarrhea, asthenia, nausea, mucositis, paresthesia and myalgia. A Phase II trial is ongoing to further investigate the activity of this new sequential treatment with doxorubicin (50 mg/m2 day 1), paclitaxel (160 mg/m2 day 2) and gemcitabine (800 mg/m2 day 6) in advanced breast cancer.