The Study of Women’s Health Across the Nation (SWAN) is a multi-site longitudinal, epidemiologic study designed to examine the health of women during their middle years. The study examines the physical, biological, psychological and social changes during this transitional period. The goal of SWAN’s research is to help scientists, health care providers and women learn how mid-life experiences affect health and quality of life during aging. The study is co-sponsored by the National Institute on Aging (NIA), the National Institute of Nursing Research (NINR), the National Institutes of Health (NIH), Office of Research on Women’s Health, and the National Center for Complementary and Alternative Medicine.