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Unified Medical Language System® (UMLS®)

MEDLINE Backfiles Source Information

The MEDLINE® Backfileswere developed and are maintained by the U.S. National Library of Medicine (NLM).

The MEDLINE database, produced by NLM, includes over 18 million journal article references related to the life sciences, with a focus on biomedicine.

MEDLINE Backfiles provide co-occurrence data for Medical Subject Headings (MeSH®) assigned to MEDLINE citations.

MEDLINE Backfiles contain MEDLINE co-occurrence data for MeSH for a five-year period ending five years ago. For example, the MEDLINE Backfiles for the 2010AA UMLS release included co-occurrence data for 2000-2004.

MEDLINE Backfiles data is located in the MRCOC.RRF file in the Metathesaurus. There are no concepts included in this source.

For more information about MeSH in the Metathesaurus, see the MeSH source synopsis.

Metathesaurus Update Frequency
MEDLINE Backfilesare updated annually.

Sites Consulted

  1. Fact sheet: MEDLINE® [Internet]. Bethesda (MD): National Library of Medicine (US); 2004 Nov 17 [updated 2010 Jun 2; cited 2010 Jul 30]. [about 6 screens]. Available from:
  2. UMLS® Reference Manual [Internet]. Bethesda (MD): National Library of Medicine (US); Chapter 3.3.10, Co-occurring Concepts (File = MRCOC.RRF); 2009 Sep [cited 2010 Jul 30]; [8 paragraphs]. Available from:

Last Reviewed: November 23, 2010