The aim of the study is to use the EQ-5D instrument to evaluate the long-term health states of women with early stage breast cancer treated by breast-conserving surgery and radiation. A total of 1,050 women treated with conservative surgery and radiation with or without systemic therapy completed 2,480 questionnaires during follow-up visits. The EQ-5D is a standardized and validated instrument for measuring quality of life outcomes. The descriptive system uses 5 dimensions of health with three possible levels of response that combine into 243 (3(5)) possible unique health states that are each assigned a values-based index score from 0 to 1. The visual analog scale (VAS) rates health on a simple vertical line from 0 to 100. Higher scores correspond to better health status. The mean index scores were 0.89 (95% CI: 0.87-0.91) at 5 years, 0.9 (95% CI: 0.86-0.94) at 10 years, and 0.9 (95% CI: 0.83-1.0) at 15 years. There were no significant differences in health states between patients by age when compared with U.S. controls. There was a statistically significant positive correlation between the results of the VAS and descriptive system. Significant trends in health dimensions over 15 years were increased problems with self-care and decreased problems with anxiety/depression, pain/discomfort, and performing usual activities. This study of EQ-5D is unique and demonstrates very high quality of life in patients long-term after breast-conserving surgery and radiation. These health states are comparable to the adult female U.S. population. These data will provide valuable patient utility information for informing decision analyses investigating new treatments in women with breast cancer.