The trilingual and structured vocabulary DeCS - Health Sciences Descriptors - was created by BIREME to serve as a unique language in indexing articles from scientific journals, books, congress proceedings, technical reports, and other types of materials, as well as for searching and retrieving subjects from scientific literature from information sources available on the Virtual Health Library (VHL) such as LILACS, MEDLINE, and others. It was developed from the MeSH - Medical Subject Headings of the U.S. National Library of Medicine (NLM) with the purpose of permitting the use of common terminology for searching in three languages, providing a consistent and unique environment for the retrieval of information regardless of the language. DeCS is a dynamic vocabulary totaling 30,895 descriptors, of which 26,225 come from MeSH, and 4670 are exclusively DeCS. There is an addition of 2032 hierarchic codes from DeCS categories in 1479 MeSH descriptors.