The aims of the General Requirements for the Competence of Calibration and Testing Laboratories are to provide a basis for use by accreditation bodies in assessing the competence of laboratories, establish general requirements for demonstrating laboratory compliance to carry out specific calibrations or test, and assist in the development and implementation of a laboratory’s quality system. DKD accredited calibration laboratories fulfil the requirements of the European standard EN 45001 (general criteria to operate a testing laboratory, May 1990) without exception. This standard is not compulsory outside Europe. The ISO/IEC Guide 25 (General requirements on the competence of testing and calibration laboratories, December 1990) is recognized instead. The EN 45001 and ISO/IEC Guide 25, also known as ANSI/NCSL Z540-1 in the United States, are identical in terms of content. They form the basis for the mutual appreciation between the European cooperation for Accreditation (EA) and its partners outside Europe. In 1999, ISO/IEC 17025 took the place of EN 45001 and ISO/IEC Guide 25 thereby eliminating any formal differences.