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Advanced Searching with MEDLINE Medical Subject Headings (MeSH)

The MEDLINE MeSH search allows researchers to build one-line simple or complex searches while using EBSCO’s many searching features. In MEDLINE, it is possible to incorporate MeSH Headings and Free Floating Headings in command line searches (searches that incorporate field codes).

What are MEDLINE Medical Subject Headings?

MeSH (medical subject headings) is the National Library of Medicine's controlled vocabulary thesaurus. Each bibliographic reference is associated with a set of MeSH terms assigned to describe the content of an article. There are more than 19,000 main headings in MeSH, as well as thousands of cross-references that assist in finding the most appropriate MeSH headings. MeSH terms are arranged in a hierarchy, or "tree structure," that permits searching at various levels of detail, from the most general to more narrow levels, to find the most precise terms. Subject specialists at the National Library of Medicine update MeSH annually.

MeSH records include indexing annotations, scope notes, entry vocabulary, history notes, and allowable qualifiers. MeSH headings can be exploded to retrieve all references indexed to the term, as well as all references indexed to any narrower term(s). Searches can be limited to Major Headings where MeSH headings indicate the main focus of an article. Searches can also be qualified with specific subheadings, to improve the precision of a search.

Referencing the Database Help File

As you begin command line searching in your MEDLINE database, you may want to review the Database Help File for your database, as an excellent resource for further information. To locate your Database Help File, open to the search page of your MEDLINE database. To the right of the Find field, next to the Search button, you will see a blue circle containing a question mark bubble. Click on this question mark to open the Help File in a new window. Scroll to the bottom of the menu on the left side of the Help file and click on the MEDLINE database name under Database Help.

Using Headings in Command Line Searching
  • Subject Heading Searching

    As with all fields it is possible to search a subject heading using the selected subject heading field code and the MeSH subject heading.

    MH - Search the exact MeSH subject heading; searches both major and minor headings

    MM - Searches the exact MeSH subject heading; searches just for major headings


    1. Search for all citations indexed with the MeSH subject heading of Tennis Elbow

      Enter: MH tennis elbow

    2. Search for all citations indexed with MeSH major subject heading of Tennis Elbow

      Enter: MM tennis elbow

  • Subject Heading Searching with Subheadings

    It is possible to search a subject heading and use subheadings. (Note: MeSH subheading two letter codes are used and are available in Database Help.)

    To search for a subject heading with subheadings (in this example Tennis Elbow with Surgery as a subheading)

    Enter: MH tennis elbow/su

    To search for a subject heading with multiple subheadings (in this example Tennis Elbows with subheadings of surgery, diagnosis, therapy)

    Enter: MH tennis elbow/su/di/th

  • Subject Heading Searching with Explosions

    It is possible to ‘explode’ a subject heading; use the + symbol

    To explode a subject heading

    Enter: MH arm injuries+

    To explode a subject heading with subheadings

    Enter: MH arm injuries+/su/di

  • Free Floating Subheadings

    MeSH subheadings can be searched independently of a subject heading. The appropriate two letter subject heading field code must be selected, as well as the two letter code for the desired subheading.

    MW – Searches for a word in the MeSH subject heading, including subheadings, retrieves citations indexed under major or minor.

    Searcher wishes to find citations that are indexed with the subheading of adverse effects, and does not care to which MeSH subject heading it is attached.

    Enter: MW ae