Reservoirs constructed near urban areas pose a high-risk potential for downstream life and property. Turkey is one of the most seismically active regions in the world and has at least 1200 large dams with different types. Major earthquakes with the potential of threatening life and property occur frequently here. The Euphrates basin studied in this article is located in a seismically very active part of Turkey. The northern part of the basin is structurally cut by numerous faults. Many large dams are located on or close to these faults. In this paper we summarize the methods used for the analysis of seismic hazards and total risk, discuss the seismic hazards of thirty-two large dams constructed on the Euphrates basin on the basis of the seismic activity of the dam site and their total risk as based on physical properties and the position in the basin. The seismic hazard analyses have indicated that peak ground acceleration changes within a wide range (0.011 g and 0.564 g) for the dam sites of the basin. A seismic hazard map showing the equivalent PGA (peak ground acceleration) values was developed so as to use for the preliminary analysis of dam structures, which will be designed in the basin. The total risk analyses depending on the seismic hazard rating of dam site and risk rating of the structure have concluded that fifteen large dams have high-risk class in the basin. These dams must be analyzed with high priority and redesigned to increase the safety of the embankments and their appurtenant structures, if necessary. (c) 2006 Elsevier B.V. All rights reserved.