The several goals of the study include: to give reliable estimates of extent to which known risk factors predict heart disease, cancers, and fractures; to identify new risk factors for these and other diseases in women; to compare risk factors, presence of disease at the start of the study and new occurrences of disease during the WHI in all study components; and to create a future resource to identify biological indicators of disease, especially substances and factors found in blood. The study enrolled 93,726 postmenopausal women and will track them for an average of nine years. Participants fill out periodic health forms and visit the clinic three years after enrollment. They take no medication and do not change their health habits.