The article describes origin and characteristics of the Italian Bioethics Thesaurus (TIB), as an example of a useful lexicon specialized in the field of Bioethics. Conceived as a supporting instrument for SIBIL (Italian Online Bioethics Information System), which is a database produced by the Documentation Service of the Italian National Institute of Health (Istituto Superiore di Sanita, ISS), TIB is currently the only example in Italy of a thesaurus entirely dedicated to the subjects of Ethics, Life Sciences and Public Health, The article also analyses some morphological, lexical and syntactic characteristics of TIB, along with the different semantic relations between controlled terms.