Journal bearings, which are used in all kinds of rotating machinery, do not only support static loads, such as the weight of rotors and load caused by transmitted torque of reduction gears, but are, in addition almost the only machine element that is able to suppress various exciting forces acting on the rotating shaft. As rotating machines have become large and multi-staged, while compactness, high speed, and high output have also been realized in recent years, not only has the bearing load increased, but also the magnitude and variety of exciting forces. Therefore, the role and importance of journal bearings have increased tremendous­ ly. In particular, for the design of rotating machines with low vibration levels and high reliability, knowledge of the exact characteristic data of bearings, and especial­ ly of the stiffness or spring coefficients and the damping coefficients of oil films in bearings, is essential. However, the amount of reliable data now applicable to practical design is limited. Through the activity of the Research Subcommittee on Dynamic Charac­ teristics of Journal Bearings and Their Applications (designated as PSC 28), estab­ lished and organized in June 1979 through May 1982 within the Japan Society of Mechanical Engineers (JSME), these coefficients, together with static characteris­ tics, have been calculated and also measured on a number of new test rigs.