Istanbul is one of the world's most ancient cities. The present population is around 13 million. The population increase rate is more than twice the average of the country, and is due to migration. Each year roughly 400.000 new inhabitants settle in Istanbul. Insufficient water sources are surrounded by unplanned and uncontrolled urban and industrial development. Thus, problems such as treatment of drinking water, sewage and wastewater, as well as transportation etc. could not be solved easily. Even though, efforts have been paid to solve these problems since 1920s, more successful activities have been realized after the establishment of Istanbul Water and Sewerage Administration (ISKI) in 1981. As a result of applying economically and technologically available systems for wastewater treatment and discharge, Istanbul today has reached to a competitive and comparable stage with other NATO member countries. In this paper, a review on the prevailing condition of the wastewater and storm water collection and treatment systems will be done and brief information on wastewater management will be given. Within the context of the study, success gained by the application of 'The Golden Horn Environmental Protection Project' and the findings of Water Quality Monitoring Studies in Golden Horn will be discussed and evaluated.