Earth scientists, who have worked together for 6 years in the priority pro gram "Hydrogeochemical Processes in the Hydrological Cycle Within the Unsaturated and Saturated Zones," have summarized the results of their research in this volume. This is the occasion to take stock and then look ahead. The priority program was set up by the Senate of The Deutsche Forschungsgemeinschaft in October 1981. This was preceded by lengthy and careful preparation by a Program Committee, and was finally recom mended by the Senate Commission for Joint Research in Earth Sciences. The main aim was the...