||Medical Subject Headings (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. There are over 27,883 descriptors in MeSH with over 87,000 entry terms that assist in finding the most appropriate MeSH Heading. In addition to these headings, there are more than 232,000 Supplementary Concept Records (SCRs) within a separate file. The MeSH thesaurus is used by NLM for indexing articles from over 5,400 of the world's leading biomedical journals for the MEDLINE®/PubMED® database.