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United States National Library of Medicine National Institutes of Health

Fact Sheet
Medical Subject Headings (MeSH®)

The Thesaurus

MeSH is the National Library of Medicine's controlled vocabulary thesaurus. It consists of sets of terms naming descriptors in a hierarchical structure that permits searching at various levels of specificity.

MeSH descriptors are arranged in both an alphabetic and a hierarchical structure. At the most general level of the hierarchical structure are very broad headings such as "Anatomy" or "Mental Disorders." More specific headings are found at more narrow levels of the eleven-level hierarchy, such as "Ankle" and "Conduct Disorder." There are 22,568 descriptors in MeSH. In addition to these headings, there are more than 139,000 headings called Supplementary Concept Records (formerly Supplementary Chemical Records) within a separate thesaurus. There are also thousands of cross-references that assist in finding the most appropriate MeSH Heading, for example, Vitamin C see Ascorbic Acid. These additional entries include 23,887 printed see references and 106,651 other entry points.

MeSH Applications

The MeSH thesaurus is used by NLM for indexing articles from 4,600 of the world's leading biomedical journals for the MEDLINE/PubMED® database. It is also used for the NLM-produced database that includes cataloging of books, documents, and audiovisuals acquired by the Library. Each bibliographic reference is associated with a set of MeSH terms that describe the content of the item. Similarly, search queries use MeSH vocabulary to find items on a desired topic.

Establishing and Updating MeSH

The Medical Subject Headings Section staff continually revise and update the MeSH vocabulary. Staff subject specialists are responsible for areas of the health sciences in which they have knowledge and expertise. In addition to receiving suggestions from indexers and others, the staff collect new terms as they appear in the scientific literature or in emerging areas of research; define these terms within the context of existing vocabulary; and recommend their addition to MeSH. Professionals in various disciplines are also consulted regarding broad organizational changes and close coordination is maintained with various specialized vocabularies.

MeSH Publication

MeSH, in machine-readable form, is provided at no charge via electronic means. The MeSH Website http://www.nlm.nih.gov/mesh is the central access point for additional information about MeSH and for obtaining MeSH in electronic form. The vocabulary is also published in print each January:

MeSH, Supplement to Index Medicus® may be ordered from the Government Printing Office (GPO): Superintendent of Documents, P.O. Box 371954, Pittsburgh, Pa. 15250-7954. Phone: (202) 512-1800; Fax: (202) 512-2250; http://www.gpoaccess.gov/index.html

Questions about the Library's MeSH program may be directed to:

Stuart Nelson, M.D.
Head, Medical Subject Headings
National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894
Phone: (301) 496-1495
Fax: (301) 402-2002
Email: nelson@nlm.nih.gov
MeSH Section home page on the Web: http://www.nlm.nih.gov/mesh

A complete list of NLM Fact Sheets is available at:
(alphabetical list): http://www.nlm.nih.gov/pubs/factsheets/factsheets.html
(subject list): http://www.nlm.nih.gov/pubs/factsheets/factsubj.html

Or write to:

FACT SHEETS
Office of Public Information
National Library of Medicine
8600 Rockville Pike
Bethesda, Maryland 20894

Phone: (301) 496-6308
FAX:(301) 496-4450
Email: publicinfo@nlm.nih.gov

Last updated: 12 January 2004
First published: 01 September 1999
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