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 study was supported by Grant No. RR0118801-01 and Contract No. N01-OD-4-2139, TO 72 between the National Academy of Sciences and the National Institutes of Health. Other contributors were the Association for Assessment and Accreditation of Laboratory Animal Care International, Canadian Council on Animal Care, Centre for Best Practice for Animals in Research (Medical Research Council, UK), Federation of European Laboratory Animal Science Associations, International Council for Laboratory Animal Science, Laboratory Animals, Ltd., and the U.S. Environmental Protection Agency. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.