Mitochondrial control region DNA sequence data were examined to determine levels and patterns of variation in 36 striped mud turtles, Kinosternon baurii, from 10 geographic locations across the species' range. Levels of sequence divergence were low, and 20 variable sites defined 18 haplotypes. Although unique haplotypes were found at most locations, several haplotypes were distributed rangewide. In particular, the putatively isolated population of the lower Florida Keys did not significantly differ genetically from the upper Florida Keys or mainland populations. Based on our analysis of 415 bp, the lower Florida Keys population either is not isolated or is very recently isolated from the remainder of the range. The lower Florida Keys population is classified as endangered by the Florida Fish and Wildlife Conservation Commission and extirpation of this population through loss of habitat seems likely. Efforts to protect suitable habitat for K. baurii, however, may increase the risk of extinction of other endangered species, such as the Key deer (Odocoileus virginianus clavium).