The use of gas turbines is increasing for producing electricity, operating airplanes and for various-industrial applications. In the last three decades, improvements in gas turbines have shown their success in increasing the amount of energy output from power stations. This is because of advances in metallurgical science and especially the materials used in gas turbines, so that it is possible nowadays to have a very efficient gas turbine with longer working life. This study has concentrated on the improvements of parameters concerned with the performances of gas turbines [i.e. net work output, thermal efficiency, specific fuel consumption (SFC), turbine and compressor efficiencies, compressor＇s inlet temperature and turbine＇s inlet temperature]. The data were taken for the Rehab power station in Jordan. The results showed that the plant improvements undertaken involve the study of a wide range of different parameters affecting the performance of the turbine, the most important of which are those which increase the plant＇s efficiency and decrease the energy cost.