OBJECTIVES: Given that treatments for advanced breast cancer are palliative rather than curative, the patient-perceived impact of chemotherapy is a critical outcome.  To date, no studies have estimated the strength of patient preferences for a comprehensive set of toxicities associated with breast cancer treatments.  The objective of this study was to measure patient preferences for treatment-related toxicities in advanced breast cancer.  METHODS: This was a cross-sectional Web-based survey of women with stage I through IV breast cancer who were recruited through web forums and newspaper ads.  Using the standard gamble approach, each participant valued her own current health state in the absence of side effects and nine health states describing that current health state plus each of nine grade III/IV toxicities.  Toxicity disutilities were calculated by subtracting the utility for current health from that for current health plus the toxicity.  RESULTS: Of the 103 patients who completed the web survey, 21 had to be excluded given irrational responses.  The mean ‘current health’ utility for the sample was 0.837.  Patients assigned higher utilities to their current health state than to the toxicity states.  Alopecia received the highest utility (mean=0.79; disutility = -4.6) of all the side effects, and diarrhea received the lowest (mean=0.69; disutility = -14.7).  Patterns were similar across disease stages, although patients with more advanced disease (stage III or IV) generally assigned lower utilities (greater disutilities) to the various toxicities. For several side effects (alopecia, nausea, vomiting, fatigue, mucositis, and diarrhea), patients who had experience with the side effect reported higher utility values compared to those who had not experienced the side effect.  CONCLUSIONS: To our knowledge, this study was the first to report strength of preferences for toxicities associated with advanced breast cancer treatments. The utilities obtained in this study may be used in future cost-effectiveness evaluations of breast cancer therapies.