Externally fired heat engines were used widely since helium the industrial revolution using dirty solid fuels for example coal, due to the lack of refined fuels. However, with the availability of clean fuels, external firing mode was abandoned, except for steam power plants. Lately, with the global trend moving towards green power production, the idea of the external fired system has captured the attention again especially externally fired gas turbine (EFGT) due to its wider range of power generation and the potential of using environment friendly renewable energy sources like biomass. In this paper, a wide range of thermal power sources utilizing EFGT such as concentrated solar power (CSP), fossil, nuclear and biomass fuels are reviewed. Gas turbine as the main component of EFGT is investigated from micro scale below 1 MWe to the large scale central power generation. Moreover, the different high temperature heat exchanger (HTHE) materials and designs are reviewed. Finally, the methods of improving cycle efficiency such as the externally fired combined cycle (EFCC), humidified air turbine (HAT), EFGT with fuel cells and other cycles are reviewed thoroughly. (C) 2014 Elsevier Ltd. All rights reserved.