Assessment of Danube River water quality must be given special attention because it is one of the most valuable water resources in Serbia and in Europe. Correlations of criteria for water quality classification were established by comparing current legislation in Serbia and Water Framework Directive of the European Union. The case study of the Danube River in Serbia includes the actual and required water quality, water quality trends, long-term-changes and multicriteria analysis of ten selected water quality parameters (PROMETHEE/GAIA). The results show that the quality of the Danube water corresponds to the descriptive indicator of “very good” water (Serbian Water Quality Index). According to the Directive 75/440/EEC, the evaluation of the eco-chemical status, corresponds to A1 category of the surface water quality intended for the abstraction of drinking water supplies. This monograph will not only serve as a tool in the integrated management and sustainability of water resources in Serbia but also for all the countries of the Danube basin.