The paper briefly reviews the problems arising in, and the system employed on, the lubrication of large modern steam-turbine electric generators. A description is given of the general layout, enumerating the various components and the reasons for their inclusion. The general qualitative relations governing the operation of film-lubricated bearings are briefly stated; published results of full-scale experiments on commercial types are compared; and a simple method is given for estimating the power absorbed, based on practical experience. Various types of oil pumps, and the principles adopted in fixing their capacity are described, the results on gear type pumps being shown by several curves. The development of modern forms of oil-cooling apparatus is traced, attention being given to factors affecting the rate of heat transmission obtainable; a series of tests carried out on a modern type are described. Curves showing the relation between heat transmission rates and oil and water velocities obtained from these tests are reproduced. The disposition, design, and capacity of oil tanks are discussed, together with the practical aspects of piping layouts. The concluding section deals with the properties of lubricants, factors contributing to deterioration, and methods of purification commonly employed.