Geothermal energy has a big importance among the renewable energy sources. In flash systems, steam quality is increased by flashing geothermal fluid. When suitable conditions exist, second flash can be used, which increases the energy production to a great extent. In double-stage flash system, selection of the first- and second-flash temperatures is very important for effective production. For the resources in Canakkale Tuzla geothermal regions, with an average temperature of 438 K and vapor content about 13%, optimum first- and second-flash temperatures were found to be 393 K and 346 K, respectively. In this study, a computer program was prepared to determine flash temperatures. It was used to find out the optimum flash temperatures which correspond to maximum work. In these calculations, the properties of Canakkale Tuzla geothermal sources in Turkey were taken as a basis.