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.

This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine.

The Institute of Medicine was chartered in 1970 by the National Academy of Sciences to enlist distinguished members of the appropriate professions in the examination of policy matters pertaining to the health of the public. In this, the Institute acts under both the Academy’s 1863 congressional charter responsibility to be an adviser to the federal government and its own initiative in identifying issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine.

Support for this project was provided by The Greenwall Foundation, the Food and Drug Administration (Award No. FDA D66112 00 95 TD 00), the Health Resources and Services Administration (Award No. 103HR941095P000-000), and the Centers for Disease Control and Prevention (Award No. 0009564092). Funds were provided by the National Institutes of Health through the National Cancer Institute (Award No. 263-MQ-436187), the National Institute of Diabetes, Digestive, and Kidney Diseases (Award No. 263-MK-521072) the National Heart, Lung and Blood Institute (Award No. 263-FJ-520288), and the National Institute of Allergy and Infectious Diseases (Award No. N01-OD-4-2139). Additional funds were provided by the U.S. Department of Defense (Award No. N00014-95-1-0920), the Charles River Laboratories, the W.R. Grace and Company-Connecticut, and the Howard Hughes Medical Institute. Additional support for dissemination of this report was provided by The Greenwall Foundation. The views presented in this report are those of the Committee on Xenograft Transplantation and are not necessarily those of the funding organizations.

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 image adopted as a logotype by the Institute of Medicine is based on a relief carving from ancient Greece.