Accreditation is the procedure by which the competence of a laboratory to perform a specified range of tests or measurements is assessed against a national or international standard. The accreditation covers the kinds of materials tested or measured, the procedures or methods used, the equipment and personnel used in those procedures, and all relevant systems that the laboratory has in place. Once accredited, the laboratory is entitled to endorse test results with their accreditation status which, if it has any validity, is an imprimatur of some degree of quality and gives the client added confidence in the results. Accreditation therefore benefits the laboratory, by allowing the laboratory to demonstrate competence in particular tests, and the client, by providing a choice of accredited laboratories that are deemed competent. Accreditation is part of conformity assessment in international trade. Conformity assessment leads to the acceptance of the goods of one country by another, with confidence borne of mutual recognition of manufacturing and testing procedures. Figure 9.1 shows the relation between accreditation and the goal of conformity in trade. For accreditation to be a cornerstones of conformity in trade, each laboratory that is assessed, in whatever country, must be judged against the same standard (e.g., ISO/IEC 17025), and the assessment process must be essentially the same from one country to another. The standards are indeed international, through the International Organization for Standardization (ISO), and the accreditation bodies themselves are scrutinized under the auspices of the International Laboratory Accreditation Co-operation (ILAC), being accredited to the ISO/IEC Standard 17011 (ISO/IEC 2004a). Full membership in ILAC is open to recognized bodies that operate accreditation schemes for testing laboratories, calibration laboratories, and inspection bodies that have been accepted as signatories to the ILAC Mutual Recognition Arrangement. They must maintain conformance with appropriate international standards such as ISO/IEC 17011 and ILAC guidance documents, and the must ensure that all their accredited laboratories comply with ISO/IEC 17025 and related ILAC guidance documents. Table 9.1 lists the full members and signatories of the ILAC Mutual Recognition Arrangement. The National Association of Testing Authorities (NATA) of Australia has the distinction of being the first accreditation body in the world (founded in 1947), and has long been in the vanguard of the approach to quality through accreditation.