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The College of American Pathologists (CAP) first published a pathology terminology called SNOP (Systematized Nomenclature of Pathology) in 1965.

SNOP has not been maintained for many year and since April 26, 2017 it is no longer licensed for use. Click here for more information ...

Versions of SNOMED

CAP broadened the scope of SNOP to cover medicine and in 1974 they published the expanded terminology with the revised name SNOMED.

An updated version called SNOMED II was released in 1979 and a further significant update was released in 1993 as SNOMED International Version 3.

SNOMED II and SNOMED International Version 3 has not been maintained since the release of SNOMED RT in 2001 and since April 26, 2017 they is no longer licensed for use. Click here for more information ...


Development of SNOMED RT (SNOMED Reference Terminology) was started in the late 1990's. This was a radical development introduced formal description logic based definitions and was released for the first and only time in early 2001.

SNOMED RT has not been maintained since its first release in 2001 and since April 26, 2017 it is no longer licensed for use. Click here for more information ...


The reason there was only ever one release of SNOMED RT was that in 1999 CAP reached an agreement with the UK NHS to merge SNOMED RT and NHS Clinical Terms Version 3. The result of this merger became SNOMED Clinical Terms (SNOMED CT).

The design of SNOMED CT built on the SNOMED RT design. It included enhancements, to enable separately maintained extension, multiple terms for concepts in different language or dialects and a formal mechanism for representing subsets.

After merging the content from the UK NHS and CAP source terminologies and removing duplicates, the initial release of SNOMED CT contained over 300,000 concepts.SNOMED CT was first released in January 2002 and since then regular updates of the SNOMED CT International Edition have been released every six months.

Notes on the Name SNOMED

Although the name SNOMED was originally derived from the phrase Systematized Nomenclature of Medicine, SNOMED is now a trademark and not an abbreviation. Therefore, the phrase and should not be used in place of or as an expansion of the formal name SNOMED. The names, "SNOMED CT" and "SNOMED Clinical Terms" are both trademarked names of the terminology and may be used interchangeably.


In 2007 all SNOMED terminologies were acquired by a new international not-for profit international body known as the International Health Terminology Standards Development Organisation (IHTSDO).

In 2012 the original SNOMED CT release format was enhanced to enable more effective history tracking (RF2 versioning) and more flexible configurations for different uses (reference sets).

IHTSDO Becomes SNOMED International

In 2017 SNOMED International became the formal trading name of IHTSDO.

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