The typical Central European urban drainage and receiving water system is described both from a historical and a technical perspective. Most common is the combined sewer system in which sanitary sewage and storm sewage are conveyed to the treatment plant in a single pipe. During storms this system is overloaded and large quantities of sewage by-pass the treatment plant as so-called combined sewer overflows (CSO) without further treatment. Sewage generating and transport processes in urban drainage systems are relatively well known. They can be simulated today with fair accuracy to predict measures against adverse effects in urban areas. Today, simulation models are an indispensable tool to describe the characteristics of CSO. Knowledge on the ecological effects of CSO is much more limited, though. There is some evidence, however, that adverse impacts to receiving water biota are primarily resulting from morphological modifications of receiving water courses rather than resulting from CSO. A future urban drainage strategy should therefore be linked to the revitalization of receiving water courses, and focus on the deceleration of storm runoff by infiltration, the separation of strong and weak sewage at the source, and the allocation of measures in a site-specific and problem-oriented manner. Storage ponds to reduce combined sewer overflows should only be applied if specific receiving water requirements can be identified.