OBJECTIVES: Metastatic breast cancer (MBC) patients are treated with a variety of regimens with differing side effects that can reduce the patients’ quality of life. Conjoint analysis is a research method used to evaluate how trade-offs are made between different attributes. This study assessed the willingness to pay (WTP) to avoid side effects related to MBC treatment using conjoint analysis.   METHODS: An online, self-administered conjoint analysis survey of US adult female MBC patients was conducted to elicit preferences for MBC treatment side effects. Attributes included in the analysis with levels described in lay terms were: Alopecia, Diarrhea, Fatigue, Nausea, Neuropathy, Pain, Neutropenia and Out of pocket costs. 15 choice-based conjoint questions were presented where patients selected the most preferred therapy. A partial profile design was used to allow for each treatment description to be made with 3 instead of all 8 attributes. The attribute choices for each question included two side effects and an out of pocket price. The survey also collected information on prior treatment regimens, previous side effect history, and demographics. RESULTS: There were 298 respondents. Most respondents were white (84%), married (57%) over 40 years of age (86%), and covered with private insurance (57%). MBC patients were WTP (US$) $3,894 to avoid severe diarrhea, $3,479 to avoid being hospitalized due to infection, $3,211 to avoid severe nausea, $2,764 to avoid severe tingling in hands and feet, $2,652 to avoid severe fatigue, $1,853 to avoid obvious hair loss and $1,458 to avoid severe pain. The most important attributes when selecting a therapy for MBC in terms of average utility were neutropenia, diarrhea and nausea. CONCLUSIONS: Patients most highly value the avoidance of diarrhea, neutropenia, and nausea with MBC treatment regimens.  Additional research with a global patient population is needed to quantify the WTP to avoid MBC side effects.