Paclitaxel (Taxol) is one of the most active drugs in the treatment of ovarian and breast cancers. Combination therapy with paclitaxel and 5-fluorouracil (5-FU) exhibits high activity in anthracycline-pretreated breast cancer, yielding response rates of 54% to 69% in recent studies. Weekly dosing of paclitaxel produces notable activity, while maintaining relatively low toxicity in heavily pretreated metastatic breast cancer patients. Uracil and tegafur (UFT) plus oral calcium folinate constitute an orally administered compound known as Orzel. This agent provides activity comparable to that of intravenously administered 5-FU plus calcium folinate, with the additional attributes of ease of administration and a more favorable side-effect profile. We initiated a phase I dose-finding trial to determine the maximum tolerated dose and dose-limiting toxicities of the combination of weekly paclitaxel by 1-hour infusion plus UFT/oral calcium folinate administered to patients with anthracycline-resistant metastatic breast cancer.