The development of the Stirling engine has recently gained momentum because of technological advances as well as the need to explore alternative power systems for meeting environmental concerns. An overview of the Stirling engine principles, taking into account the ideal as well as the actual cycle, is presented. The analysis examines the various design aspects and the performance and emission characteristics. A comparison is made between the Stirling and other continuous and cyclic combustion engines, such as the gasoline, diesel, gas turbine, and steam engines. This includes recent designs for the Rankine cycle and gas turbine combustors being considered for automotive applications.