OBJECTIVES: The objective of this analysis was to assess patients’ willingness to pay (WTP) for a reduction in risk of breast cancer treatment side effects. METHODS: A survey was developed using continent valuation processes to assess the WTP for a reduction in side effects. The survey asked female MBC patients to provide the amount they were willing to pay for a 25%, 50% and 100% reduction in risk of the following side effects: diarrhea/dehydration, hair loss, fatigue, nausea, neutropenia/febrile neutropenia, pain and tingling in hands and feet. Patients were also asked to select the side effect they would pay the most to avoid. Demographic information such as age, race/ethnicity, region, employment status, insurance type, and treatment regimen was also collected. RESULTS: A total of 202 metastatic breast cancer patients completed the survey. The majority of respondents were white, married, over the age of 51, and well educated. Most respondents had private insurance (67%) or Medicare (24%). Of those who reported paying out of pocket for their last treatment (58%), the average payment was $459. For a 25%, 50%, and 100% reduction in the risk of side effects, respondents were willing to pay an extra $1886, $3837 and $7794, respectively. Hair loss (28%), pain (17%) and nausea (15%) were selected most often as the side effect respondents would pay the most to avoid. CONCLUSIONS:  Patients with MBC highly value reduction in treatment side effects and are WTP 4.2 times more for a treatment devoid of side effects over a treatment with a 25% reduction in the risk of side effects.  Additional research is warranted to quantify WTP for specific side effects.