The article aims at illustrating the characteristics and functions of a monolingual thesaurus, focusing on the Italian Thesaurus of Bioethics (Thesaurus Italiano di Bioetica, TIB) the controlled vocabulary used to index and retrieve documents within SIBIL (Italian Online Bioethics Information System). TIB includes controlled terms (descriptors) translated from the Bioethics Thesaurus adopted by the Kennedy Institute of Ethics of the Georgetown University of Washington and revised according to the Italian context of study and scientific debate in the field of bioethics. The overall amount of TIB terms consists in over 1600 headings. Methods to link thesaurus terms hierarchically, by association and by showing synonyms as recommended in ISO standards are applied with reference to descriptors drawn from TIB. Future plans to make the English version of TIB available online within European networks are also illustrated, aiming at spreading information relating to bioethics at an international level.