Laboratory accreditation is that part of the conformity assessment process that recognizes the technical competence of laboratories providing calibration or test data. A2LA accredits all types of laboratories (except medical laboratories) and thus provides one place where a laboratory can achieve accreditation for all of its testing and calibration activities.

During 2001, A2LA continued the transition from ISO/IEC Guide 25-1990, "General Requirements for the Competence of Calibration and Testing Laboratories" to its replacement, ISO/IEC 17025, with the goal of completing the transition for all labs by December of 2002. The general requirements, the conditions for accreditation (the laboratory's commitment), and a description of the accreditation process are maintained in A2LA's document General Requirements for Accreditation of Laboratories (known as the green booklet for the color of its cover).

Because of the needs of users (users of accredited laboratories) and specifiers (organizations that require accreditation, including government and private sector), specific technical criteria have been developed to amplify the requirements of the general criteria (ISO/IEC Guide 25 and ISO/IEC 17025) for several of the programs and fields of testing and calibration.

A separate Scope of Accreditation is given for each field. It lists specific tests, types of tests, or calibrations for which the laboratory has been found competent. For laboratories that perform a large variety of testing, a Supplemental Scope of Accreditation was previously provided so that the user can see if the laboratory has been recognized as competent for a particular method. However, beginning in mid-2000, the Supplement was being phased out in favor of a multi-page Scope, and by the end of 2001, most laboratories were being issued the new multi-page document. For calibration laboratories, scopes of accreditation also include a description of the laboratory's capabilities in terms of measurement parameter, range, best measurement capability expressed as an uncertainty, and technique and/or equipment.

The application for accreditation describes the many technical fields and programs for which a laboratory may apply. These include the programs listed in Table 1.