Technical milestone - Medical subject headings used to search the biomedical literature

The National Library of Medicine's MEDLINE (MEDLARS Online) database was th e first database to be searched nationwide via value-added telecommunicatio n networks. Now available on the World Wide Web free of charge from the Nat ional Library of Medicine and from many other sources, it is the world's mo st heavily used medical database. MEDLINE is unique in that each reference to the medical literature is indexed under a controlled vocabulary called M edical Subject Headings (MeSH). These headings are the keys that unlock the medical literature. MeSH multiplies the usefulness of the MEDLINE database and makes it possible to search the medical literature as we do today. Thi s paper commemorates the 40th anniversary of the introduction of MeSH and s alutes some of the farsighted persons who conceived and developed the MEDLI NE database.