In the 1990s, General Electric Power Systems and Siemens Westinghouse Power Corporation, spurred by the U.S. Department of Energy’s Advanced Turbine System Program, undertook the development of an advanced gas turbine systems (ATS), an energy technology that significantly outperformed the state-of-the-art technology at the time, achieving high thermal efficiencies with low nitrogen oxides emissions. The story of how these two turbines manufacturers went about the development of these advanced turbine systems is the subject of this paper. Advanced turbine systems reflect a major advance in the efficiency, moving from around 53% efficiency in the early 1990s to 60% efficiency in 2001. Such an improved efficiency represents a significant change in that a single percent point thermal efficiency can reduce operating costs by as much as USD 20 million over the life of a typical gas fired combined cycle power plant of 400 to 500 megawatts (MW) (Green, 1999)