Unified Medical Language System® (UMLS®)
UMLS - Release Documentation Archive
Current Release Documentation
Note: As of the 2009AA UMLS Release, general reference information is available as the UMLS Reference Manual. Information specific to a UMLS Release, such as sources included in the current version of the Metathesaurus and statistics regarding the number of concepts, remains on the UMLS Web site as part of the Release Documentation.
Previous UMLS Releases
*Archived from 2014AA-present.