The encompassing aim of the European Science Foundation Programm "Environments and Ecosystem Dynamics of the Eurasian Neogene (EEDEN)" is the detailed analysis of the response of terrestrial ecosystems to environmental change through the integration of multidisciplinary studies focussing on some selected, already fairly well-known "high-resolution" time intervals in the Neogene of the Eurasian realm. This volume presents some results of a symposium held in November 2002 in Frankfurt/Main (Germany). Detailed analyses of the time interval HRI 3-the "Middle Miocene Crisis" are challenging and rewarding, as it comprises the first phase in the development of the later Neogene terrestrial ecosystems, expressed, for instance, in the mammal record by a major turnover and successive immigration events.