In the summer of 2008, three sporadic cases of E. coli O157:H7 occurred in children. Isolates cultured from stool specimens collected from the children were genetically indistinguishable. There was no common food or water exposures for the illnesses. By the end of October, nine cases were known. All children were found to have some recreational exposure to Evergreen, Colorado play fields. There had been frequent reports of elk droppings on the play fields. E. coli O157:H7 was isolated from elk droppings, and it matched the strain of E. coli O157:H7 that had been isolated from the children.