A total of 86 children treated for injuries that occurred while playing in water from fire hydrants are described. Patients were urban (100%), minority (97%) children with few alternative means for keeping cool. Injuries occurred on extremely hot summer days (mean maximum temperature 36.3 degrees C [97.5 degrees F]). Laceration of the foot on broken glass was the most common injury and was prevented by wearing footwear (P less than .001). Motor vehicles caused all serious injuries. Sprinkler attachments on the hydrants were associated with significantly fewer motor vehicle-related injuries (P less than .001) and water pressure-related injuries (P = .02). Adults were present at more than 90% of injury scenes, but had no effect on the safety of fire hydrant play. Public policy should be directed toward increasing the availability of alternative means for keeping cool, increasing the number of hydrants equipped with sprinklers, and reducing the amount of broken glass in the streets. Public education targeting adults to remove glass from the street, insist that children wear footwear, and open only those hydrants that have sprinklers could further reduce injuries to urban children who play in water from fire hydrants.