Protecting the River Rhine always means dealing with a complex international system of environment, economic and transport policy problems. About 50 million people live and work in the Rhine catchment area. Since 1950 the governments of Switzerland, France, Germany, Luxembourg and The Netherlands have co-operated in the International Commission for the Protection of the Rhine against Pollution (ICPR). So far, three phases characterize this co-operation. During the first phase up to the mid-seventies joint work was developed and organised, learning processes about national efforts took place and the first inventory of the hot spots was conducted. The second phase comprises the period from the signing of the Convention on the Protection of the Rhine against Chemical Pollution to the fire at the Sandoz warehouse at the end of 1986. It was characterized by efforts to determine international threshold values for extremely hazardous substances. The third phase will be terminated at the same time as the Rhine Action Programme in 1999. Its most important target is the return of higher species, such as the salmon, to the Rhine. In December 1994 the Conference of Rhine Ministers has to decide about next phase. It is expected that its beginning will be marked by a new improved Bern Convention.