This document, a revision of the 1996 edition of NIST SP 903: Directory of U.S. Private Sector Product Certification Programs, presents information on 122 private sector groups in the United States which engage in product certificaiton activities. Entries describe: the type and purpose of each organization: the nature of the activity; a pictorial representation of the organization's mark (if available); products certified; standards used; certification requirements; any accrediation of recognition by a U.S. or foreign private sector or government agency; availability of services; methods of cost determination; and other relevant details. This directory is part of an ongoing NIST effort to establish and maintain comprehensive information on standards, regulations, certification programs and related topics. This material has been compiled to meet the needs of government, industry, and the public for information on private sector product certification programs in accordance with the requirements of the U.S. Trade Agreements Act of 1979 and other relevant legislation.