The Pohrenk fluorite deposit is hosted by sedimentary rocks of Eocene and Miocene age. The distribution of fluorite ores is controlled by the unconformity plane between Eocene and Miocene sediments. The origin of host carbonate minerals and of fluorite-hosted fluid inclusion waters have been investigated from a stable isotopic point of view. Carbonates have delta(13)C((PDB)) values ranging from 2,2 parts per thousand to -7,6 parts per thousand and delta(18)O((PDB)) values ranging from -7,0 parts per thousand to -11,0 parts per thousand. The hydrogen and oxygen isotope compositions of the fluid inclusion-hosted waters have a relatively restricted range of deltaD((SMOW)) (-33 to -42 parts per thousand) and delta(18)O((SMOW)) values (-2,5 to -6,1 parts per thousand). The isotopic composition of carbonates and fluid inclusion waters indicate that fluorite deposition occurred as a result of circulation of formation waters in a paleokarst environment.