During its passage through the City of Berlin (Germany), the quality of the River Spree is strongly influenced by combined sewer overflows (CSO), which lead to critical oxygen concentrations (DO) every year and to occasional larger fish kills. A continuous integrated monitoring concept, using state-of-the-art online sensors, was planned and started in spring 2010. It combines (i) continuous measurements of the quality and flow rates of CSO at one main CSO outlet downstream of the overflow structure and (ii) continuous measurements of water quality parameters at five sites within the urban stretch of the receiving River Spree. The first monitoring results show that continuous water quality measurements in CSO outlets and at downstream river stations are possible at high accuracy, even for comparably complex parameters such as chemical oygen demand (COD). Analysis of measured data confirms the significance of CSO discharges on receiving waters and underlines the value of continuous measurements in describing the local dynamics of the CSO and their impacts on water bodies.