Index Medicus (IM) was a comprehensive bibliographic index of scientific journal articles focusing on medical science fields, published from 1879 to 2004. It was initiated by John Shaw Billings, head of the Library of the Surgeon General's Office, United States Army. This library later evolved into the United States National Library of Medicine (NLM). In the 1960s, the NLM began computerizing the indexing work by creating MEDLARS, a bibliographic database, which became MEDLINE. Index Medicus thus became the print presentation of the MEDLINE database's content, which users accessed usually by visiting a library which subscribed to Index Medicus (for example, a university scientist at the university library). It continued in this role through the 1980s and 1990s, while various electronic presentations of MEDLINE's content also evolved, first with proprietary online services (accessed mostly at libraries) and later with CD-ROMs, then with Entrez and PubMed. As users gradually migrated from print to online use, Index Medicus print subscriptions dwindled. During the 1990s, the dissemination of home internet connections, the launch of the Web and web browsers, and the launch of PubMed greatly accelerated the shift of online access to MEDLINE from something one did at the library to something one did anywhere. This dissemination, along with the superior usability of search compared with use of a print index in serving the user's purpose (which is to distill relevant subsets of information from a vast superset), caused the use of MEDLINE's print output, Index Medicus, to drop precipitously. In 2004, print publication ceased. In one sense, Index Medicus and Abridged Index Medicus still exist conceptually as content curation services that curate MEDLINE content into search subsets or database views (in other words, subsets of MEDLINE records from some journals but not others), but this is irrelevant to most use of MEDLINE.
Index Medicus publication began in 1879 and continued monthly through 1926, with a hiatus between 1899 and 1902. During this hiatus, a similar index, the Bibliographia medica, was published in French by the Institut de Bibliographie in Paris. The Index Medicus was amalgamated with the American Medical Association's Quarterly Cumulative Index to Current Literature (QCICL) as the Quarterly Cumulative Index Medicus (QCIM) in 1927 and the AMA continued to publish this until 1956. From 1960 to 2004 the printed edition was published by the National Library of Medicine under the name Index Medicus/Cumulated Index Medicus (IM/CIM). An abridged version was published from 1970 to 1997 as the Abridged Index Medicus. The abridged edition lives on as a subset of the journals covered by PubMed ("core clinical journals").
The last issue of Index Medicus was published in December 2004 (Volume 45). The stated reason for discontinuing the printed publication was that online resources had supplanted it, most especially PubMed, which continues to include the Index as a subset of the journals it covers.
Inclusion into the Index is not automatic and depends on a journal's scientific policy and scientific quality. These criteria are evaluated by the "Literature Selection Technical Review Committee" and the final decision is made by the NLM director. The review process may include outside reviewers and journals may be dropped from inclusion.
- "FAQ: Index Medicus Chronology". Retrieved 2009-09-06.
- "History of Historical Collections - History of Medicine - National Library of Medicine". Retrieved 2009-09-06.
- "Abridged Index Medicus Ceasing Publication". Retrieved 2009-09-06.
- "FAQ: Finding a List of Abridged Index Medicus or Index Medicus Journal Titles". Retrieved 2009-09-06.
- "'Index Medicus - NLM Technical Bulletin to Cease as Print Publication". National Library of Medicine - NLM Technical Bulletin. 2004-05-04. Retrieved 2008-04-16.
- "Number of Titles Currently Indexed for Index Medicus and MEDLINE on PubMed". Retrieved 2009-09-06.
- "How are journals selected for Index Medicus and MEDLINE?". Retrieved 2009-09-06.
- "LSTRC". Retrieved 2009-09-06.
- NLM Catalog Search Limits The "Journal Subsets" limit provides the options "Index Medicus journals (IM)" and "Core clinical journals (AIM)" to restrict search results to journals contained in Index Medicus and Abridged Index Medicus respectively.