The effects of urban runoff used to recharge groundwater basins in the Fresno, Calif., area are discussed. The study, which was part of the US Environmental Protection Agency’s nationwide urban runoff program, was undertaken to determine the environmental effects on groundwater quality and to identify management practices that would mitigate adverse effects. No deterioration of groundwater quality because of recharge with runoff was found, although the authors recommend a more thorough investigation of the effects of recharge with runoff from industrial sites.