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A study of the Badenian (Middle Miocene) marine deposits of Hungary yielded a rich bryozoan fauna of 238 species comprising 59 cyclostomes, 176 cheilostomes, and 3 ctenostomes. Six palaeobiogeographic groups have been identified among this fauna on the basis of the present-day and fossil distribution of the species. Similarities within the Central Paratethys and between the Central Paratethys, the Mediterranean and the Atlantic have then been calculated using Jaccard's index. The results indicate strong affinities between the Central Paratethyan basins of Hungary, Austria, Poland, and Romania. The higher number of species and the lower level of endemism observed in Hungary is explained by the vicinity of this basin to the entrance of the water seaway connecting the Mediterranean to the Paratethys. A decrease in taxonomic diversity between the Early and the Late Badenian is also observed …