Journal selection criteria are studied for international databases MEDLINE and EMBASE and also LILACS, which covers only Latin-american and Caribbean biomedical production but follows exhaustive selection criteria that are widely reported. The three databases consider subject suitablility, quality of contents, quality of editorial work, production quality, selection methods of proposed articles, type of contributions, language and geographic coverage and other additional requirements included by some of them and not specified by others. The selection criteria of international databases are compared applied to the Spanish biomedical journals indexed by MEDLINE, EMBASE or both. Presently, 41 Spanish journals are indexed by MEDLINE, and 111 by EMBASE, being 28 titles common to both. Regarding the number of journals indexed in both databases, we can assume that the criteria used by MEDLINE are more restrictive than those used by EMBASE. Special consideration is given to the 13 Spanish journals indexed by MEDLINE and not by EMBASE. Finally, after studying journals indexed by the Spanish databases IBECS (Indice Bibliográfico Español de Ciencias de la Salud) and IME (Indice médico Español), conclusions are shown implying that their selection criteria must be based in those applied by MEDLINE or EMBASE.Peer reviewed