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NLM Classification 2017: Worldwide source of medical library classification

Search Help

Finding Terms:
  • enter term(s) in the search box; searches are left-truncated, i.e., if you enter Leg, you will also retrieve Legislation, for example, unless you use quotes
  • exact match searching: enclose the term(s) in quotation marks, e.g.: "gene therapy"; terms with quotes and terms without quotes may be combined in a single search
  • "Current Page" search option on all pages of the Index (1-8, A-Z) and all pages of the Schedule (QS-WZ): from the Home page, go to the Index or Schedule, select the appropriate page (each letter of the Index and each Class in the Schedule are separate "pages") and select the "Current Page" radio button below the search box; this improves retrieval speed; it can be combined with the quoted search
  • the search is carried out on the entire Index or Schedule unless you select the "Current Page" option
  • capitalization is ignored (not case-sensitive)
  • punctuation is ignored; terms may be searched with or without hyphens, commas, etc.; punctuation is also ignored in terms in quotation marks
  • you may truncate terms (see 'Further Details on Searching,' below)
  • you may input apostrophes if in MeSH, or you may truncate, e.g.: Addison Disease, or just: Addison (but not misspelled as Addisons; see 'Further Details on Searching,' below
  • boolean operators are not used— multiple terms are automatically ANDed together (but there is no 'phrase' or 'proximity' searching—see 'Retrieval Display' below)
  • order is not important (except in a quoted or exact match search)
  • the system initially defaults to an Index search
  • you may select an Index search or a Schedule search by clicking the corresponding button below the search box
  • subsequent searches default to Index or Schedule depending on the previous selection

Finding Classification Numbers:

  • to search for a class number in the Schedules, use the class number search box

Retrieval Display: Your terms will appear enlarged in the display

In an Index Search:

  • the system retrieves any Index entry (i.e., a main heading plus its subheadings, or a reference) containing term(s) matching your search
  • to retrieve an exact match, enclose terms in quotation marks
  • you can restrict your search by selecting the "Current Page" option
  • except in the case of exact match searches, the automatic ANDing of multiple terms does not imply proximity between any terms within the text of a retrieved Index entry—although all will be present
  • click on the blue shaded class numbers to hyperlink to the appropriate location in the Schedule (see ' Important Note' below)
  • hyperlinked cross references and see references also display in blue
  • click on the 'tree' icon to the left of the Index term to jump to the descriptor details in the MeSH browser (definition, annotation, allowable qualifiers, etc.)
  • if the number of hits is too great or too small, retry using different terms—retrieval depends on character string matches—not concepts (try searching the MeSH Browser first)

In a Schedule Search (term search):

  • the system retrieves any line with matching term(s)
  • to retrieve an exact match, enclose terms in quotation marks
  • you can restrict your search by selecting the "Current Page" option
  • hyperlinked cross-references and see references display in blue—click to jump to the referred term (see 'Further Details on Retrieval,' below)


  • each letter of the Index and each Class in the Schedule can be searched individually by selecting the "Current Page" option
  • pages may be scanned directly using up or down arrows
  • press ‹control›‹home› to go to top; ‹control›end› to go to bottom of page
  • use browser forward and back buttons as needed

Important Note: Only those Index terms within the domain of the NLM Classification are hyperlinked to the Schedules; some terms are classed using the Library of Congress Scheme—these numbers are provided as a convenience to users, but this system does not verify the accuracy of LC class numbers. Please check current LC Schedules in these instances.

Further Details on Searching: Enter search term(s) as completely as possible, truncating the term, i.e., omit any plural and other endings, for example, if unsure. For example: while Women's Health can be entered exactly, it can also be retrieved by typing wom hea (but not misspelled womens health without the apostrophe). However, bear in mind that a truncated search may retrieve other items beginning with the given letters—so take this into account when searching. To find an exact match, use quotes around your term(s); to limit retrieval to a particular letter of the Index or Class of the Schedule, use the "Current Page" option.

Further Details on Retrieval: In the NLM Schedules, the retrieval display shows the lines containing your search term(s), with the matching term(s) enlarged. All class numbers shaded in blue are hyperlinked to their actual appearance in the Schedule; in addition, references to the geographic Table G are linked to the table itself.