Pseudemys turtles are an important component of southeastern North American aquatic ecosystems, but the relationships within the genus are poorly understood. Convergent morphology and apparent hybridization have complicated the identification of species boundaries and have resulted in numerous conflicting taxonomic treatments. We used mitochondrial DNA sequence data from the control region and cytochrome-b gene to address 1 ) the monophyly of currently recognized subgeneric clades (the cooters and the red-bellies), and 2) relationships within these two groups. A total of 91 specimens representing 8 Pseudemys and 3 outgroup taxa were sampled, and 36 distinct haplotypes were recovered. Pseudemys forms a well-supported monophyletic group, but relationships among species were not well resolved, such that support for the two subgeneric groupings was lacking. Furthermore, most taxa do not appear to be monophyletic, with the exception of P. gorzugi (Rio Grande Cooter) and P. texana (Texas Cooter), suggesting the possibility of mitochondrial introgression as a result of historic or continuing hybrid swarms across the range of the genus, or the lack of resolution may reflect a pattern of recent speciation. In light of recent molecular surveys in turtles, the utility of mitochondrial DNA in turtle systematics is also discussed .