The diagnostic features of Plagiognathus are clarified, with characteristics of the male genitalia being used for the first time in diagnosing the Nearctic species. The North American species are revised, with a total of 86 native and 3 introduced species being recognized. Twenty-four species are described as new. Habitus, vesical, and antennal illustrations are provided for all of these species. The Palearctic fauna is discussed; vesical illustrations are provided for 10 of the 24 species placed in Plagiognathus in the most recent catalog.

Twenty-five new synonymies are created. Twenty-five species are transferred into Plagiognathus from other genera or removed from Plagiognathus and placed in other genera; in addition to the new combinations with definitive generic placement, 16 species are treated as incertae sedis. Microphylellus Reuter, Chaetophylidea Knight, and Parapsallus Wagner are treated as junior synonyms of Plagiognathus.Plagiognathus reuterellus, new name, is proposed to replace Plagiognathus flavipes Reuter, 1875, a junior secondary homonym. Six neotypes and one lectotype are designated in an effort to ensure stability in the application of names within Plagiognathus.

A new genus, Tuxedo, with Microphylellus bicinctus Van Duzee, as the type species, is described to accommodate five previously described taxa that do not belong to either Microphylellus or Plagiognathus, in which genera they were originally placed. The generic-group name Zophocnemis Kerzhner is elevated to generic status to accommodate its single included species, bicolor Jakolev, because that species does not fit the revised diagnosis for Plagiognathus. Myochroocoris Reuter is synonymized with Atractotomus Fieber, its single included species, griseolus Reuter from eastern North America, having all of the diagnostic characters of Atractotomus.

Specimens were broadly sampled from North American museums, with particular attention paid to the fauna west of the Great Plains. The eastern North American fauna is, nonetheless, treated in detail with the most extensive attempt yet to deal with the fauna of the South.

Many new host records are included, clarifying associations for some species, but still leaving the breeding habits of others in question.