ABSTRACT The Women's Health Initiative (WHI) is one of the largest and most complex disease prevention studies ever conducted. Educating prospective participants about the study and obtaining informed consent is a sequential, multicomponent process, consisting of verbal and written information, a video, and the reading and witnessed signing of the informed consent forms. All informed consent materials were reviewed by study investigators, local Institutional Review Boards; the WHI Data and Safety Monitoring Board; the Women's Health Initiative Policy Advisory Committee; the National Institutes of Health; the Institute of Medicine in Washington, D.C.; focus groups of postmenopausal women; and the media. The consent process continues to be dynamic; as more is known about potential risks and benefits associated with participating in the WHI, the consent process has and will be revised accordingly.