ISO/IEC 17025 General requirements for the competence of testing and calibration laboratories is the main ISO standard used by testing and calibration laboratories. In most countries, ISO/IEC 17025 is the standard for which most labs must hold accreditation in order to be deemed technically competent. In many cases, suppliers and regulatory authorities will not accept test or calibration results from a lab that is not accredited. Originally known as ISO/IEC Guide 25, ISO/IEC 17025 was initially issued by the International Organization for Standardization in 1999. There are many commonalities with the ISO 9000 standard, but ISO/IEC 17025 is more specific in requirements for competence and applies directly to those organizations that produce testing and calibration results and is based on somewhat more technical principles.. Laboratories use ISO/IEC 17025 to implement a quality system aimed at improving their ability to consistently produce valid results. It is also the basis for accreditation from an accreditation body.
There have been three releases; in 1999, 2005 and 2017. The most significant changes between the 1999 and 2005 release were a greater emphasis on the responsibilities of senior management, explicit requirements for continual improvement of the management system itself, and communication with the customer. It also aligned more closely with the 2000 version of ISO 9001 
The 2005 version of the standard comprises five elements; Normative References, Terms and Definitions, Management Requirements, and Technical Requirements. Management requirements are primarily related to the operation and effectiveness of the quality management system within the laboratory. Technical requirements include factors that determine the correctness and reliability of the tests and calibrations performed in the laboratory.
The 2017 version of ISO/IEC 17025 has modified this structure to be Scope, Normative References, Terms and Definitions, General Requirements, Structural Requirements, Resource Requirements, Process Requirements, and Management System Requirements. General Requirements and Structural Requirements are related to the organization of the laboratory itself. Structure Requirements cite those issues related to the people, plant, and other organizations used by the laboratory to produce its technically valid results. Process Requirements are the heart of this version of the standard in describing the activities to ensure that results are based on accepted science and aimed at technical validity. Management System Requirements are those steps taken by the organization to give itself quality management system tools to support the work of its people in the production of technically valid results.
Some national systems (e.g. UKAS M10 in the UK) were the forerunners of ISO/IEC 17025:1999 but could sometimes be exceedingly prescriptive. ISO/IEC 17025 allows laboratories to carry out procedures in their own ways, but an auditor (assessor) may require the laboratory to justify using a particular method.
In common with other ISO quality standards, ISO/IEC 17025 requires continual improvement. Additionally, the laboratory will be expected to keep abreast of scientific and technological advances in relevant areas.
In common with other accreditation standards of the ISO 17000 series (and unlike most ISO standards for management systems), third party auditing (assessment) of the laboratory is normally carried out by the national organization responsible for accreditation. Laboratories are therefore accredited under ISO/IEC 17025, rather than certified or registered (c.f. ISO 9000 series).
In short, accreditation differs from certification by adding the concept of a third party (Accreditation Body (AB)) attesting to technical competence within a laboratory in addition to its adherence and operation under a documented quality system, specific to a Scope of Accreditation.
In order for accreditation bodies to recognize each other's accreditations, the International Laboratory Accreditation Cooperation (ILAC) worked to establish methods of evaluating accreditation bodies against another ISO/CASCO standard (ISO/IEC Guide 58 - which became ISO/IEC 17011). Around the world, geo-political regions such as the European Community, and Asia-Pacific, the Americas and others, established regional cooperations to manage the work needed for such mutual recognition. These regional bodies (all working within the ILAC umbrella) include European Accreditation Cooperation (EA), the Asia Pacific Laboratory Accreditation Cooperation (APLAC), Southern Africa Accreditation Cooperation (SADCA) and the Inter-American Accreditation Cooperation (IAAC).
The first laboratory accreditation bodies to be established were National Association of Testing Authorities (NATA) in Australia (1947) and TELARC in New Zealand (1973). Most other bodies are based on the NATA/TELARC model include UKAS and British Cert.in the UK, FINAS in Finland and DANAK in Denmark to name a few.
In the U.S. there are several, multidisciplinary accreditation bodies that serve the laboratory community. These bodies accredit testing and calibration labs, reference material producers, PT providers, product certifiers, inspection bodies, forensic institutions and others to a multitude of standards and programs. These ILAC MRA signatory accreditation bodies carry identical acceptance across the globe. It does not matter which AB is utilized for accreditation. The MRA arrangement was designed with equal weight across all economies. ABs include:
- The ANSI-ASQ National Accreditation Board and their recent acquisitions of L-A-B and ASCLD-LAB which are now both [http://www.anab.org/ ANAB
- The American Association for Laboratory Accreditation (A2LA)
- Perry Johnson Laboratory Accreditation (PJLA)
- American Industrial Hygiene Association
- International Accreditation Service, Inc. (IAS)
- National Voluntary Laboratory Accreditation Program (NVLAP) - technically part of the US government and only accredits a few narrow disciplines
- American Society of Crime Laboratory Directors-Laboratory Accreditation Board (ASCLD-LAB) which is now ANAB (see above).
In Canada, there are two accreditation bodies:
The accreditation of calibration laboratories is the shared responsibility of the Standards Council of Canada (SCC) Program for the Accreditation of Laboratories-Canada (PALCAN), and the National Research Council of Canada (NRC) Calibration Laboratory Assessment Service (CLAS). The CLAS program provides quality system and technical assessment services and certification of specific measurement capabilities of calibration laboratories in support of the Canadian National Measurement System.
In other countries there is often only one Accreditation Body. Typically these bodies encompass accreditation programs for management systems, product certification, laboratory, inspection, personnel and others:
- National Accreditation Board for Testing and Calibration Laboratories (NABL) (India)
- Komite Akreditasi Nasional (KAN) (Indonesia)
- Irish National Accreditation Board (INAB) (Ireland)
- International Accreditation New Zealand (IANZ) (New Zealand)
- Dutch Accreditation Council (DAC) (The Netherlands)
- Bureau of Accreditation (BoA) (Vietnam)
- Korea Laboratory Accreditation Scheme (KOLAS) (South Korea)
- DAkkS (Germany)
- "Principles behind ISO/IEC 17025" (PDF). Canadian Association for Laboratory Accreditation (CALA). Retrieved 27 March 2018.
- Honsa, Julie D.; Deborah A. McIntyre (2003). "ISO 17025: Practical Benefits of Implementing a Quality System". Journal of AOAC International. 86 (5): 1038–1044. Retrieved 28 February 2012.
- "ISO/IEC 17025 Comparison - 1999 to 2005". SAI Global Limited ABN. Retrieved 28 February 2012.
- "NATA - NATA Field and Program Accreditation Criteria - ISO-IEC 17025 Laboratory Accreditation (Applicable to all ISO/IEC 17025 fields)". www.nata.com.au. Retrieved 2017-04-28.
- "Testing Laboratory Registration Council Of New Zealand" (PDF).
- "About A2LA". American Association for Laboratory Accreditation. Retrieved 28 February 2012.
- "ISO/IEC 17025:2005 – Laboratory Accreditation Program- PJLA". Retrieved 29 May 2015.
- "About IAS | The International Accreditation Service". Retrieved 29 May 2015.
- "ASCLD-LAB home page". American Society of Crime Laboratory Directors-Laboratory Accreditation Board. Retrieved 12 July 2012.
- "CALA". Retrieved 29 May 2015.