Hexastylis, here considered distinct from Asarum, is endemic to the southeastern United States. New or revised descriptions of ten species and five varieties are presented along with a new, dichotomous key. Three subgeneric groups—Arifolia, Speciosa, and Virginica—are recognized. Morphological, biogeographical, and phenological data indicate that the Virginica group of Hexastylis may be divided into three closely related subgroups: Virginica, Heterophylla, and Shuttleworthii. Species in the Heterophylla subgroup (heterophylla, minor, and naniflora) seem to be the most closely related and are, therefore, the most difficult to separate taxonomically. Within the three subgroups, species barriers are maintained by geographical isolation, while between subgroups, gene flow seems to be prevented by phenological isolation.