Recent randomized trials have indicated that the risks of hormone therapy for menopausal women may outweigh the benefits. The purpose of this study was to describe how health plans responded to the findings of the Women's Health Initiative (WHI) estrogen plus progestin trial. We surveyed five health plans affiliated with the HMO Research Network and the Cancer Research Network to document the response of each plan to the WHI in terms of patient and provider education and guidelines. Every health plan issued responses within 3 months of WHI's termination in a variety of formats. Recommendations were relatively consistent across the organizations. Given the documented changes in hormone therapy use in these five health plans in the post-WHI era, we conclude that attempts on the part of each organization to educate patients and providers about the implications of the WHI may have contributed to the observed changes in hormone therapy use.