The geothermal fluid of the North German Basin is currently used for both heat and power generation. Due to the combined effect of high temperature inherent to geothermal operations and the high salinity present in this hydrothermal fluid corrosion and scaling susceptibility become very important aspects to consider for material selection in these technical facilities. Preliminary evaluation of the materials suitability represents therefore a valuable strategy to ensure a secure and reliable operation of them. Nevertheless until now corrosion resistance of possible construction materials for technical equipment involved in exploration as well as construction and production facilities in this highly saline geothermal fluid that has temperatures above 140 °C was evaluated only in the laboratory using artificial conditions. Based on these results high-alloyed materials such as super austenitic stainless steels and nickel-based alloys were recommended. In order to confirm this one long-term exposure test was conducted in Gross Schoenebeck a well located in the geothermal area of the North German Basin. This paper discusses the observed corrosion and scaling behavior of different metallic materials including low-alloyed steels stainless steels and cemented carbides in the geothermal fluid of the North German Basin during actual service conditions.