The genus Peyerimhoffia Kieffer (type-species Sciara vagabunda Winnertz), currently classified as a subgenus of Cratyna Winnertz (type-species Cratyna atra Winnertz) is redefined and its phylogeny studied by parsimony analysis. Cladistic analysis using sixty-four morphological characters from adult males of sixty-six ingroup and one outgroup species produced thirty most parsimonious cladograms. The strict consensus cladogram of these showed unambiguously that the type-species of Peyerimhoffia and the species currently referred to the Corynoptera crassistylata group form a monophyletic unit. The phylogenetic hypothesis obtained also suggested that Cratyna s.l. in its current concept is non-monophyletic and that Peyerimhoffia deserves generic status. The genus is Holarctic-Oriental in distribution and includes the following species, which are keyed and described or diagnosed: Peyerimhoffia alpina (Mohrig) (Austrian Alps, Italy, Spain, Canada: Quebec), P. calva sp.n. (Nepal), P. collina sp.n. (Russia: Altay region), P. crassistylata (Frey) (central and northern Europe, Altay region, Kurile Islands), P. curvata (Mohrig & Mamaev) (Russia: Tuva region), P. infera sp.n. (northern Europe), P. ioculatoria (Mohrig) (Nepal), P. menzeli sp.n. (northern Europe), P. obtusicauda (Strobl) (southern Europe), P. semicurvata (Mohrig) (Nepal, Burma), P. subcurvata (Mohrig) (Nepal), P. thula sp.n. (northern Europe), P. ultima sp.n. (Nepal), and P. vagabunda (Winnertz) (Europe, eastern Palaearctic). Plastosciara perniciosa Edwards, Hyperlasion curtipennis Edwards, and Plastosciara hybrida Mohrig & Mamaev are excluded, the former appearing more closely related to Epidapus Haliday, the latter two to Spathobdella Frey.