The phylogenetic and phylogeographic relationships of the North American cyprinid genus Erimystax were examined using sequences of the mitochondrial cytochrome b gene. Phylogenetic analyses were performed using parsimony and Bayesian approaches. Relationships within the genus were (((Erimystax cahni plus Erimystax x-punctatus)(Erimystax dissimilis plus Erimystax harryi))(Erimystax insignis))). Genetic distances among species were high and suggest that all speciation events occurred during the Miocene. Shallow divergence and wide geographic distribution in both E. x-punctatus and E. dissimilis suggest post-Pleistocene dispersal. Erimystax x-punctatus expanded its range northward into the upper Mississippi basin and eastward into the Ohio River basin from a putative Ozarkian refugium. Erimystax dissimilis expanded its range northward from a southern Appalachian refugium.