Concern about the global environment and the need to make effective use of energy resources are driving plans to utilize the latest technology to upgrade the key components used in existing hydroelectric power plants with the aim of improving operating efficiency and increasing output. One example of this is a project in the USA to upgrade large 300-MW class pump-turbines and generator-motors originally installed in the 1970s. To improve the characteristics of a pump-turbine, the turbine profile is designed by using the latest flow simulation techniques to obtain a detailed understanding of the flow dynamics. The results of this work allow the pump-turbine equipment to be upgraded to meet the needs of current operation.