Two children were hospitalized due to infections with an identical strain of E. coli O157:H7. The only common link identified between the cbhildren was that they had both visited a petting zoo in Arizona. No common food or beverage was consumed by the two children at the zoo, and the children were not related. One child had direct contact with petting zoo animals; the second child had contact with exterior railings, but not with the animals. Both children had played in an area immediately adjacent to, and downhill from, the petting zoo facility. The same strain of E. coli O157:H7 was identified in the stool of petting zoo animals. Upon notification of the results, zoo officials immediately closed the petting zoo and adjacent play area.