Research and development of high bypass ratio turbofan engines have been conducted in Japan since 1971. Three prototype engines have been built and tested and have met design specifications. The project is conducted under the National Research and Development Program of the Japanese Government. The engineering background of the project's initiation is reviewed. The purpose and management of the system are discussed. The objectives and master schedule as well as engine specifications and design features of the engine are presented. The state of development of the engine, including performance data and problems encountered, are reviewed.