During the last decades increased human activities have had a large impact on water quality of watercourses in Europe. A deterioration of water quality has mainly been caused by agricultural and industrial activities. To keep track of the environmental situation in watercourses continuous supervision and assessment is needed. Achieving a standardized environmentally sustainable water quality within the European Union requires a uniform assessment of watercourses. To develop a uniform assessment of watercourses within the European Union is the major task. Existing watercourse classification methods within each European country need to be evaluated and compared. As one step of the evaluation procedure, this study investigates and compares watercourse classification methods in Sweden and Germany. In Sweden “Environmental Quality Criteria” are used to classify both current status and human influence. In Germany water quality is assessed by a biological-ecological method based on Saprobiesystem and a complex chemical index as well as defined target values in order to assess water chemistry. The Swedish method allows to investigate the cause of environmental problems because every parameter is assessed separately. However, no information about the overall water quality can be obtained. In contrast, the German chemical index describes the overall water quality but does not assess single parameters separately. Cause and extent of environmental problems are therefore not explicitly stated. A case study that was part of this study shows that the German and the Swedish watercourse classification methods give potentially different results if evaluated for the same watercourses. The German method always classifies the watercourses with a lower classification class that stands for a better water quality. The results probably reflect the difference between the methods to set classification scales and class limits used in every country. An explanation of the different classes could be that German watercourses generally are more polluted than Swedish ones. Both different natural conditions and different environmental problems require different assessment methods. If it will be possible to develop a new and uniform assessment system throughout Europe is debatable. The investigation arrives at the conclusion that it will be difficult to develop one appropriate system for all European countries. Considering both large differences between existing assessment methods in the countries and different natural conditions within Europe it will take a long time to develop an equitable and environmentally sustainable assessment method as it is required within the European Union.