I. Examine the response rate of HER2-positive metastatic breast cancer to combination therapy with trastuzumab and BMS-247550 in two cohorts of women: a. women who have received no prior chemotherapy or trastuzumab for their metastatic breast cancer; b. women who have received prior trastuzumab therapy (either for metastatic disease or prior adjuvant trastuzumab if < 1 year since completion of adjuvant trastuzumab therapy) and up to 2 prior chemotherapeutic regimens in the metastatic setting.