Abstract: A method and apparatus are disclosed for determining steam quality wherein heat is added to or removed from a sample flow of steam to reach a point of superheating or subcooling. The amount of energy required to superheat or subcool the sample is factored in with other parameters such as steam flow rate, temperature and pressure to determine the quality of the steam. The steam quality sensor has many applications in equipment such as turbines, heat exchangers, condensers and the like.