The objectives of this report on the amphibians and reptiles of Illinois are threefold. The first is to provide a critical review of the species and subspecies known to inhabit Illinois. The second is to present detailed distributional information for these animals in the hope that the data may contribute to the knowledge of the ecology and biogeography of Illinois. The third is to call attention to variation trends that I have discerned within Illinois and that will enable future investigators to utilize character analyses for populations occurring in limited parts of the state.