This work analyses the options to achieve interoperability among different library databases so they can be searched from a single Web interface. The databases object of this research are the ones used in The Fernandes Figueira Institute Library, which is a branch of FIOCRUZ specialized in Maternal and Child Health. Library users generally look for medical decision support information. The Library users preferred databases are LILACS, MEDLINE and ACERVOS ONLINE FIOCRUZ. All of them use the DeCS and MeSH Thesaurus to subject description. Each of these databases are analyzed in aspects as access points, bibliographic description and display formats, in order to identify common elements. Technologies and standards to achieve interoperability as Z39.50 and OAI-PMH protocols, meta-search engines, Dublin Core Metadata Set BIREME’s metaIaH meta-search engine are also analyzed.  From this analysis emerged three conceptual models to achieve interoperability among the three databases, evolving two actors, the search interface – SI, and the information resources (the three databases) - IR: Effort Sharing, between SI and IRs; Concentrated Effort in the RIs; and Concentrated Effort in the SI to achieve interoperability. The three models are compared, outlining the advantages and disadvantages of each one to achieve interoperability among the databases of interest to Fernandes Figueira Institute Library.