A reconstruction of the phylogenetic relationships is presented for the holarctic Nephrotoma dorsalis-group, comprising 47 species. Their relationships are analyzed according to the principles of Hennig (1966), briefly outlined under ‘Methods’. Discussed are the outgroups of Nephrotoma and of the dorsalis-group, their sister groups however could not be established yet. The copulation-mechanism of crane flies is described, followed by a discussion of the structures involved in both sexes, allowing a better understanding of the observed character changes. A total of 99 characters was used to work out the phylogeny. The monophyly of the dorsalis-group and of most species-groups could therefore be based on more than one synapomorphy. The most primitive members of the dorsalis-group are found in the eastern Palaearctic. Remarkable is the monophyletic origin of all the nearctic species (the macrocera-group). The phylogeny of the group will be the base for a biogeographic analysis, dealt with in a forthcoming paper.