Thirty species of the genus Lygocoris Reuter known to occur in Canada and Alaska are reviewed. Lygocoris confusus (Knight) is considered to be a synonym of L. contaminatus (Fallen), communis var. novascotiensis (Knight) is a synonym of communis (Knight), caryae var. subfuscus (Knight) is a synonym of caryae (Knight), and canadensis var. binotatus (Knight) is a synonym of canadensis (Knight). The species considered are: pabulinus (Linnaeus), lucorum (Meyer), alni (Knight), artricallus Kelton, atritylus (Knight), belfragii (Reuter), canadensis (Knight), caryae (Knight), clavigenitalis (Knight), communis (Knight), contaminatus (Fallen), fagi (Knight), geneseensis (Knight), hirticulus (Van Duzee), inconspicuus (Knight), invitus (Say), johnsoni (Knight), knighti Kelton, laureae (Knight), omnivagus (Knight), ostryae (Knight), parrotti (Knight), piceicola Kelton, quercalbae (Knight), semivittatus (Knight), tiliae (Knight), univittatus (Knight), viburni (Knight), vilticollis (Reuter), and walleyi Kelton.A key to species, brief redescriptions, illustrations of species and male claspers, distribution maps, and host plants are included. A list of the remaining 10 species known from the United States is appended.