Irrigation district modernization is required to provide adequate water delivery service to farms if modern on-farm irrigation technologies are to be widely adopted worldwide. Within the last 10 years throughout the western U.S., there has been a rapid expansion of modernization efforts by irrigation districts, although it has certainly not been universal. Worldwide, however, only a few excellent examples of sustainable irrigation district modernization efforts exist. Social problems, inequity, and lack of reliability are key issues in international projects, while in the U.S., modernization efforts have focused on improved flexibility of water delivery service, and have often been driven by efforts to improve the environment or to transfer water. Because irrigation districts in the U.S. are so varied, the specific appropriate modernization activities vary by district.