Participating Centers: Clinical centers (principal investigators) in the SWAN include the University of Michigan, Ann Arbor (MaryFran Sowers, PhD); Massachusetts General Hospital, Boston (Robert Neer, MD, 1994-1999; Joel Finkelstein, MD, 1999-present); Rush University, Rush University Medical Center, Chicago (Lynda Powell, PhD); University of California, Davis/Kaiser (Ellen Gold, PhD); University of California, Los Angeles (Gail Greendale, MD); University of Medicine and Dentistry, New Jersey Medical School, Newark (Gerson Weiss, MD, 1994-2004; Nanette Santoro, MD, 2004-present); and the University of Pittsburgh (Karen Matthews, PhD). The National Institutes of Health (NIH) program offices included the National Institute on Aging, Bethesda, Maryland (program officers, Marcia Ory, PhD, 1994-2001; Sherry Sherman, PhD, 1994-present), and the National Institute of Nursing Research, Bethesda. The central laboratory was at the University of Michigan (Daniel McConnell, PhD, Central Ligand Assay Satellite Services). The coordinating centers (principal investigators) were the New England Research Institutes, Watertown, Massachusetts (Sonja McKinlay, PhD, 1995-2001), and the University of Pittsburgh (Kim Sutton-Tyrrell, DrPH, 2001-present). Chris Gallagher, PhD, and Susan Johnson, MD, were Steering Committee chairs.