
A second release-ISO/IEC 17025:2005-was made on after it was agreed that it needed to have its wording more closely aligned with the 2000 version of ISO 9001. ISO/IEC 17025:1999 was issued by the ISO in late 1999 and was internationally adopted in 2000. However, the ISO decided to convert the guide into a standard and introduce tight compatibility with ISO 9001, which was also being revised, such that ISO 9001 would be treated as a master standard and the next evolution of Guide 25 to be treated as a standard to be specifically applied to testing and calibration laboratories.

Guide 25 was created with the belief that "third party certification systems should, to the extent possible, be based on internationally agreed standards and procedures." In the mid- to late 1990s, an update to Guide 25 was required. ISO/IEC 17025 was originally known as ISO/IEC Guide 25, first released in 1978, with subsequent editions following in 19.
