Skip to Content
United States National Library of Medicine National Institutes of Health

Leasing Journal Citations (MEDLINE®/PubMed® including OLDMEDLINE)

Data Content
MEDLINE, the primary component of PubMed®, is the NLM's premier citation database. MEDLINE's subject scope is biomedicine and health, broadly defined to encompass those areas of the life sciences, behavioral sciences, chemical sciences, and bioengineering.

MEDLINE citation data comprises approximately 93% of the data distributed to MEDLINE/PubMed licensees. The other categories of records that reside in PubMed and are distributed to licensees are:
  1. the out-of-scope citations from a few selectively indexed MEDLINE journals (primarily covering general science and general chemistry) for which the life sciences articles are indexed for MEDLINE;
  2. in-process citations which provide a record for an article before it is indexed with MeSH and added to MEDLINE or converted to out-of-scope status;
  3. some citations in the OLDMEDLINE subset that have not yet been updated with current vocabulary and converted to MEDLINE status;
  4. some citations in PubMed that precede the date a journal was selected for MEDLINE indexing if the citations are submitted to NLM electronically by the publishers;
  5. starting in summer 2005, prospective citations to articles from non-MEDLINE journals that submit full text to PubMed Central and are thus cited in PubMed.

NLM now exports over 98% of PubMed records to MEDLINE/PubMed licensees. The approximately 2% of the records not exported to MEDLINE/PubMed licensees are those tagged [PubMed - as supplied by publisher] in PubMed. These are mostly records recently added directly to PubMed via electronic submission from a publisher, most of which are soon to proceed to the next stage, at which time the record will be exported. Most other non-exported records are either: older citations for the relatively few non-MEDLINE journals in PubMed; citations to MEDLINE journals prior to their date of selection for MEDLINE which were submitted electronically by the publishers before late July 2003; or citations electronically submitted for articles that appear on the Web in advance of the journal issue's release (i.e., ahead of print citations). Following publication of the completed issue, the item will be queued for issue level review and released in In-Data-Review status. All "publisher-supplied" citations have not been reviewed for accurate bibliographic data.  Also see the Fact Sheet "What's the Difference Between MEDLINE and PubMed?".

The <PubmedData> group of elements that reside in PubMed records are not distributed to NLM licensees.

NLM does not provide search software.

Specifications and Access
NLM distributes MEDLINE/PubMed in XML format via ftp. See MEDLINE Characters for information on use of diacritical marks and UTF-8 encoding. Links to the DTDs and other information/documentation, including MEDLINE/PubMed XML data element descriptions, are available.  Also see MEDLINE/PubMed Data.

A completely maintained MEDLINE/PubMed baseline database containing over 17 million records is available each December.

Each year's baseline database is a complete reload for continuing licensees (it is unlikely NLM will offer an alternative option of end-of-year changed records-only in the future). The current (2008) baseline database requires 60.2 GB disk space uncompressed; 7.8 GB compressed. Subsequent update files distributed after the baseline files contain new, revised, and deleted records. They are generally available five days each week and should be applied by licensees regularly.

In addition to, or instead of, mounting the XML data locally, licensees have access to the MEDLINE/PubMed Baseline Repository (MBR) Query Tool which is available from a link on the MBR main page. The MBR home page contains links to various freely accessible resources; however the Query Tool is restricted to NLM’s registered MEDLINE/PubMed licensees. The MBR Query Tool provides Web access to the baseline databases 2002 and forward. It permits searching by MeSH Headings, Subheadings, MeSH Heading/Subheading combinations, Names of Substances (MeSH Supplementary Concept Records), and PMID. Users can limit or filter by Date Created, Date Completed, Date Last Revised, Publication Year, and Status. Citations retrieved are available in both XML Format and PubMed’s MEDLINE ASCII Display Format.

Sample NLM Data
Sample MEDLINE/PubMed data are available. A license agreement is not needed for sample data.

How to Lease
NLM leases MEDLINE/PubMed to U.S. individuals or organizations; to its formally recognized International MEDLARS Centers; and to non U.S. individuals or organizations for internal research projects with no commercial citation search service. There is no charge for leasing NLM data from NLM. For purposes of leasing NLM databases, the following criteria must be met to be considered a U.S. organization: the organization is incorporated in U.S.; the signing official is a principal in the organization who is located in the U.S. and is not simply an authorized agent; and any financial payment to the NLM is issued from an U.S. account (although there are no fees for leasing NLM databases in the foreseeable future).

To lease, complete and return the applicable License Agreement and the Intended Use Worksheet.

The end of the each MEDLINE production year is mid-November and the new year's baseline files will be available for complete reload approximately one month later. Depending on the time of year, prospective licensees may wish to consider waiting until December to first lease the data to avoid a reload of the new year's files shortly after initial receipt of the data. New license requests received each November and December will be processed for receipt of the next year's completely maintained baseline files near the end of December. See Additional Information below.

Obtain NLM's usage report form for submission at the end of the U.S. Federal Government fiscal year, i.e., after September 30.

MEDLINE licensees must retain a minimal set of data elements.

Alternatives to Leasing
MEDLINE/PubMed may be downloaded for personal use and a single copy of downloaded data may be redistributed. Small amounts of MEDLINE/PubMed data may be retrieved from PubMed for redistribution without entering into a formal licensing agreement. See Information on Copyright for additional details.

Additional Information
MEDLINE/PubMed update files contain new and revised versions of records, and deleted records. Update files are generally available to licensees at noon EST Tuesday-Saturday. During several weeks each November and December only records in in-data-review and in-process status are distributed as NLM prepares for and performs annual data maintenance. Various types of maintenance actions, sometimes affecting large numbers of records, also take place during the year. Thus, licensees should process the revised records as well as new and deleted records in the update files regularly.

Announcements and documentation for licensees are posted at the Information for Licensees of NLM Data page. Licensees are also encouraged to read the NLM Technical Bulletin and to subscribe to NLM's e-mail alert, NLM-Announces.

The MeSH Vocabulary, a companion database for MEDLINE, may be downloaded at no cost after completion of a brief Memorandum of Understanding.

Information about journals cited in MEDLINE/PubMed is found in:
  1. The List of Serials Indexed for Online Users available in PDF and XML format and the List of Journals Indexed for MEDLINE (these publications do not cover OLDMEDLINE journal titles)
  2. LocatorPlus and NLM Catalog, the NLM's online catalog
  3. Serfile, another file that may be leased from NLM (see http://www.nlm.nih.gov/databases/leased.html)
  4. PubMed journals files (contains limited journal information; updated daily)
  5. Entrez Journals database for basic journal information similar to data found in PubMed journals list (available in the Entrez Utilities; updated daily).

Last updated: 10 June 2008
First published: 29 November 2005
Metadata| Permanence level: Permanence Not Guaranteed