NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

Support for this project was provided by Agency for Healthcare Research and Quality, American Medical Association, Association of American Medical Colleges, BlueCross/BlueShield Association, Burroughs Wellcome Fund, Centers for Disease Control and Prevention, Centers for Medicare and Medicaid Services (formerly HCFA), Department of Veterans Affairs, Doris Duke Charitable Foundation, Food and Drug Administration, Johnson & Johnson, Merck and Company, National Institutes of Health, Pfizer, Inc., and the Robert Wood Johnson Foundation. The views presented in this report are those of the authors and are not necessarily those of the funding agencies.

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The serpent has been a symbol of long life, healing, and knowledge among almost all cultures and religions since the beginning of recorded history. The serpent adopted as a logotype by the Institute of Medicine is a relief carving from ancient Greece, now held by the Staatliche Museen in Berlin.