OBJECTIVES: The Women’s Health Initiative (WHI) estrogen+progestin (E+P) clinical trial provides a large sample to estimate health state utility values for post-menopausal women with an intact uterus in the United States. To facilitate future health economic evaluations in this large population sub-group, we estimated utilities for trial participants stratified by age group (50-59, 60-69, 70-79) and randomization assignment (E+P or placebo).  METHODS: We measured health state utility values for all 16,608 trial participants with the Short Form-6D (SF-6D) utility index using a validated Bayesian mapping algorithm and U.S. weights. We calculated cross-sectional mean baseline and 1-year utilities, and mean within-patient utility change from baseline to 1-year. Patients included in the baseline analysis completed the SF-36 within 7 days of randomization, and those included in the 1-year and change analyses completed the SF-36 within 30-days of their 1-year follow-up date. RESULTS: All patients contributed to the baseline analysis, and approximately 47% contributed to the 1-year and change analyses. At baseline, mean SF-6D values for all patients 50-59, 60-69, and 70-79 were 0.744 (SD=0.113), 0.743 (SD=0.105), and 0.722 (SD=0.101), respectively. At 1-year, E+P arm mean values were 0.754 (SD=0.117), 0.751 (SD=0.117), and 0.725 (SD=0.109), and placebo arm mean values were 0.751 (SD=0.122), 0.748 (SD=0.109), and 0.716 (SD=0.106), respectively. The E+P arm mean changes were -0.008 (SD=0.106), -0.004 (SD=0.096), and 0.000 (SD=0.093), and the placebo arm mean changes were 0.000 (SD=0.105), -0.003 (SD=0.095), and 0.011 (SD=0.093), respectively.  CONCLUSIONS: We found minimally decreasing utilities among older age groups, and little variability between utilities by hormone replacement therapy use. These results may be particularly useful in future health economic evaluations of aging women given that they are derived from a large randomized sample, and age group specific.  However, our findings may be limited by the homogeneity and representativeness of the E+P trial participants.