The geologie term "'Tethys" introduced by Eduard Suess (1893) into Reience waR originally a paleogeographic one. Since its original des­ eription it has been used in various ways. One of them is Tethys as a paleo-biogeographie eoneept. This eoneept was adopted for IGCP Project 262, Tethyan Cretaeeous Correlation. It was proposed by G. CSASZAR and Heim; A. KOLLMANN and has been approved by the IGCP Board in February 1987. The projeet haR its aimH primarily in the improvement of the stra­ tigraphie cOl'relation between the heterogenous faeies of the Tethyan realm. The requests to paleontology in this programme are of variouR kindH: The delimitation of the Tethyan realm in spaee and time needH a dear statements on the eomposition of Tethyan faunal 01' floral assem­ blages. Riozones based on various fossil groups have to be eRtablished fOI' biostratigraphie eorrelation. Finally, Tethyan bioprovinees have to be established.