The geologic term "Tethys" introduced by Eduard Suess (1893) into science was originally a paleogeographic one. Since its original description it has been used in various ways. One of them is Tethys as a paleo-biogeographic concept. This concept was adopted for IGCP Project 262, Tethyan Cretaceous Correlation. It was proposed by G. Czaszar and Heinz A. Kollmann and has been approved by the IGCP Board in February 1987. The project has its aims primarily in the improvement of the stratigraphic correlation between the heterogenous facies of the Tethyan realm. The requests to paleontology in this programme are of various kinds: The delimitation of the Tethyan realm in space and time needs clear statements on the composition of Tethyan faunal or floral assemblages. Biozones based on various fossil groups have to be established for biostratigraphic correlation. Finally, Tethyan bioprovinces have to be established. These problems have been discussed in a special meeting of the paleontological group of the project which was held on January 25-27, 1988, in Vienna. Papers presented at this meeting are published in this volume.