The relationship of two species of Neonectria associated with beech bark canker in North America was evaluated by comparing isolates of these and additional species of the Neonectria coccinea (Pers.:Fr.) Rossman & Samuels group found on Fagus. Gene regions in the translation elongation factor 1-alpha (EF1-α), RNA polymerase II second largest subunit (RPB2), and β-tubulin were sequenced and analyzed. Results indicate that the fungus associated with beech bark disease previously known as Neonectria coccinea var. faginata Lohman et al. (≡ Nectria coccinea (Pers.:Fr.) Fr. var. faginata Lohman et al.) should be recognized as a separate species, Neonectria faginata , distinct from Neonectria coccinea . Neonectria faginata including its anamorphic state, Cylindrocarpon faginatum C. Booth, is known only on Fagus in North America. A second species associated with beech bark disease in North America is Neonectria ditissima (Tul. & C. Tul.) Samuels & Rossman, which can be distinguished morphologically from Neonectria faginata based on ascospore size, conidial size and shape, and colony pigmentation. Morphological and molecular data indicate that Neonectria ditissima represents an older name for Neonectria galligena Bres. Similarly, the anamorphic state of Neonectria ditissima is the older epithet Cylindrocarpon heteronema with Cylindrocarpon willkommii as a synonym. Neonectria ditissima occurs on a variety of hardwood trees in North America and Europe. Neonectria coccinea occurs only on Fagus in Europe. Neonectria major (Wollenw.) Castl. & Rossman is recognized as a species that occurs only on Alnus in Canada (British Columbia), France, Norway, and the United States (Washington). The following nomenclatural changes are proposed: Neonectria faginata comb. and stat. nov., Neonectria fuckeliana comb. nov., Neonectria hederae comb. nov., Neonectria major comb. and stat. nov., and Neonectria punicea comb. nov.