The APAT library makes for the first time available for the scientific community the ThIST (Thesaurus Italiano di Scienze della Terra - Italian Thesaurus of Sciences of the Earth) in bilingual version, Italian and English. It is the result of a nearly total revision of the thesaurus born by the integration among the terminological database of the former Library of the Italy Geological Service (today APAT Library) and the thesaurus published by the CNR in 1997. It is tightly connected to the Multilingual Thesaurus of Geosciences (MTG), realized by the International workgroup MTG, in which Italy is represented by APAT. It is already used for the cataloguing of the biblio-cartographic material (monographs, articles of periodicals, papers) possessed by the Library and the recovery of the related information.