Variable-speed pumps an: becoming increasingly commonplace in the water distribution industry, replacing conventional fixed-speed pumps. while the principal benefit is reduced energy consumption and power costs, there ate other significant advantages, including reduced leakage. This paper focuses on some of the economic and hydraulic benefits of using variable-speed pumps to improve the operation of water distribution systems, by presenting several examples that are intended to emphasize calculated results illustrating these benefits. In particular, a direct calculation of pump speeds to meet desired operating conditions exactly, a determination of optimal pump speeds for the most energy-efficient operation of water distribution systems, and an illustration of controlling potentially damaging transients are presented. These examples make use of a state-of-the-art optimization method based on genetic algorithms. along with the recent advances in hydraulic modeling technology.