The UMLS is provided free to all users.

Users of the SPECIALIST Lexicon & Lexical Tools and the Semantic Network should read the terms of use before using either product.

Semantic Network Terms of Use

Lexical Tools Terms of Use

Metathesaurus users are required to complete a license agreement before downloading the product files.

Users should read Appendix 1 in the Metathesaurus documentation before using any vocabulary. Sixty-seven percent of the content in the Metathesaurus is unrestricted for US use and distribution. The remaining content contains vocabularies which have additional licensing requirements.

Metathesaurus users are required to file a brief annual report summarizing their use of the Metathesaurus at the end of the calendar year. This information is used to improve the Metathesaurus.

Metathesaurus License Agreement