The phylogeny and biogeography of the western Palaearctic species of Nephrotoma are analyzed. Phylogeny is dealt with in a cladistic sense. Briefly outlined are criteria developed for polarity decisions as well as the rôle assigned to parallelisms. Representatives of fourty-one Holarctic (sub)genera were examined in order to establish the sistergroup of Nephrotoma. The internal hypopygial stuctures of these taxa are discussed and the following cluster of closely related taxa is recognized: Dolichopeza s. str., Oropeza, Nesopeza, Prionocera, Trichotipula, and Scamboneura, Nephrotoma. The two last-mentioned taxa are considered sistergroups. The western Palaearctic Nephrotoma species are assigned here to four monophyletic groups: cornicina group, dorsalis group, brevipennis group, and crocata group. In the section dealing with biogeography, an attempt is made to correlate the phylogeny of the cornicina and crocata groups with glacial-interglacial cycles. In a further account the distribution patterns of all Palaearctic species are discussed in relation to Pleistocene and Holocene climatic fluctuations. The origin of the genus is situated in early Tertiary East Asia. The brevipennis group, restricted to Madeira, is assumed to date back from at least Pliocene times. The dorsalis group, widespread throughout the Holarctic, apparently achieved its present range before the late Pliocene. It is intimated that the Pleistocene climatic oscillations had little effect on speciation within groups adapted to northern temperate or even cooler climates. This in contrast to the southern temperate and Mediterranean species groups such as the flavescens and crocata subgroups. The relative success of these two subgroups in post-Cromerian times may well be associated with their shift to more open habitats.