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Unified Medical Language System® (UMLS®)

US Edition of SNOMED CT®

Note: The US Edition provides a single source of SNOMED CT content for use in the United States. The US Edition is a standalone release that combines the content of both the US Extension and the International release of SNOMED CT. For additional information regarding ONC Regulations please see this ONC FAQ.


Updates to the US Edition will be available approximately one month after publication of the International Release of SNOMED CT.


Current US Edition Data Files

March 2015
RF2 Release (431 MB)
RF1 release (159 MB)

*Please note - these release files were updated July 22, 2015*

Release Notes: In addition to 839 new concepts specific to the US, the March US Edition of SNOMED CT also contains all of the content from the January 2015 International Release of SNOMED CT. The US Edition is the official source of SNOMED CT for use in US healthcare systems.

Please note, that similar to the International release, the US Edition RF1 and RF2 release files are now available as two separate downloads. The SNOMED CT RF2 to RF1 Conversion files and additional RF1 files can now be found on the SNOMED CT Permanent Packages page


Previous US Edition Data Files


File Name and Download LinkRelease DateRelease NotesFile Size
US Edition of SNOMED CT (RF1 and RF2 versions) September 2014 In addition to 378 new concepts the September US Edition of SNOMED CT also contains all content from the July 2014 International Release of SNOMED CT. Additionally, the release contains the most recent update of the SNOMED CT to ICD-10-CM mapping file. 560 MB
US Edition of SNOMED CT (RF1 and RF2 versions) March 2014





The US Edition of SNOMED CT is the official source of SNOMED CT for use in US healthcare systems.  It is comprised of:

  • The International Release of SNOMED CT
  • The US Extension to SNOMED CT, a formal extension to the International Release containing US-specific content (concepts, descriptions, relationships, and history).

The main purposes of the US Edition are to:

  • Provide “rapid” access to concept IDs for use by implementers, pending action by IHTSDO on content submissions likely to be added to the International Release of SNOMED CT.
  • Provide standard terminology needed for US clinical use cases, but not generally useful in other countries, e.g., regulatory or legislatively mandated terms specific to the US.
  • Eliminate the need to combine the US Extension with the International Release thus avoiding potential data integrity problems resulting from concepts in the US Extension referencing parent concepts only available in the International Release.

The International Release of SNOMED CT will continue to be separately available to UMLS Licensees from the SNOMED CT downloads page.  The US Extension to SNOMED CT will no longer be provided as a separate file after March 2013; US Extension content will only be available through the US Edition of SNOMED CT.   

The US Edition was developed to facilitate the use of SNOMED CT as the primary coding terminology for clinical information in electronic health records, research databases and clinical trial databases, except in the domains of medications and tests, which are covered by RxNorm and LOINC respectively.  As local vocabularies often provide variable ways of representing commonly used concepts, the use of a common list of SNOMED CT concepts will maximize data interoperability among institutions.  The US Edition streamlines installation and use of US-specific SNOMED CT content found in the US Extension.  Users unable to find terms they think are appropriate should submit additional SNOMED CT content requests to NLM through the US SNOMED CT Content Request System (USCRS).

Note: The March 2013 Release of the US Extension will mark the last time that NLM will make the standalone US Extension files available for download. For future releases, users must download the US Edition to obtain US Extension content.


Related Documents

File description
The US Edition of SNOMED CT is distributed in two formats:  Release Format 1 (RF1), and Release Format 2 (RF2).  US Edition files correspond to SNOMED CT files as described in the SNOMED CT® Technical Implementation Guide, International Release.

Update and maintenance
A new version of the US Edition will be published approximately one month after each new release of the International Release of SNOMED CT. A history file will be provided with each release of the US Edition to document the type and resolution of changes to the US-specific content.

SNOMED CT license requirement
SNOMED CT is owned by the International Health Terminology Standards Development Organisation (IHTSDO), of which NLM is the US Member. Use of SNOMED CT is subject to the IHTSDO Affiliate license provisions (incorporated in the License Agreement for Use of the UMLS® Metathesaurus® as Appendix 2) and is free in IHTSDO Member countries including the United States, in low income countries, and for Qualifying Research Projects in any country.

Feedback and suggestions
We welcome any questions, comments or suggestions that would improve the quality, accuracy and usability of the extension. Please send feedback via the NLM Customer Service form. Please be sure to include the subject line "SNOMED CT US Edition."

We would like to thank and acknowledge the contributions of Julie Green and Jeff Wilcke of the Veterinary Terminology Services Laboratory at Virginia Tech, and Ian Green and Ian Arrowsmith of the United Kingdom Terminology Centre for their expertise and advice during the development of the US Extension. We also thank all past and current UMLS licensees who have submitted content for consideration to the US Extension and their continued input and data that define the extension content.