OBJECTIVE: To compare paclitaxel (pac) and docetaxel (doc) in the treatment of second line or greater metastatic breast cancer using a cost-effectiveness analysis. METHODS: Costs were collected prospectively from 31 patients in a single outpatient center. Direct medical costs were collected (e.g. all medications, physician/clinic/laboratory visits, ER, hospitalizations, home health care, consultations, special procedures, transfusions, phone calls, and miscellaneous) and costs were defined using Medicare reimbursement rates and AWP for drugs. Effectiveness measures were obtained from two phase III trials conducted by Nabholtz. Sensitivity analyses are currently underway. RESULTS: The average cost per cycle of chemotherapy was $4,298 and $2,869 for doc and pac respectively. The objective response rates (OR) obtained for doc and pac in the phase III trials were 30% and 26% respectively. The cost-effectiveness (CE) ratio for doc is $14,327 per one-percent increase in OR. The CE ratio for pac is $11,035 per one-percent increase in OR. An incremental CE analysis suggests that using doc costs $35,725 per one-percent increase in OR compared to pac. CONCLUSIONS: The cost-effectiveness ratios suggest that pac is the more cost-effective choice. The incremental cost-effectiveness analysis still supports the use of pac; however, doc is not out of the standard range of payment for gains in effectiveness. Physicians and third party payers should use this information along with cost-utility studies to help guide decisions on treatment for metastatic breast cancer patients.