The main objective of the rain enhancement program implemented in Israel over the past 24 yrs is augmentation of its scarce water resources. The program comprises randomized cloud seeding experiments and operational seeding. A method of evaluating the hydrological effectiveness of this program by a rainfall-runoff method has recently been developed and applied to 26 water sources (springs and streams) within the Galilee target area. Double regression analysis was performed on each water source, first between the runoff and its catchment-basin rainfall in the target area and then between the same runoff and a control rainfall. Comparisons were made between seeding and pre-seeding periods, identifying changes related to cloud seeding as distinct from other systematic changes. The Jackknife technique was used to determine the statistical significance of the runoff increments. Evaluation for the last 13 yrs of cloud seeding indicates only weak overall runoff increase, though results of individual sources were not rated adequately significant. Median runoff increments for the six target zones range from 0 to 14%, whereas power calculations show that runoff changes higher than 20-25% could have been detected by this method.