The paper reviews the trends in the development of hydroelectric generating equipment for conventional and pumped-storage plants over the past 25 years. The growth in unit capacities, sizes and operating head ranges is outlined for various types of turbines. The features in generator design required to meet the growth of unit capacities are discussed for low-speed and high-speed machines. This review includes trends in hydraulic, mechanical and electrical design which have made the growth a reality. The mechanical and electrical auxiliaries, such as governors, static excitation equipment, static protection relays, digital controls, pump-motor starting and braking equipment, are also discussed.