The molecular analysis of the Filarioidea and the endobacteria Wolbachia is no more limited to the agents of human diseases and the diversified sampling permits a synthesis with the morphological and biological results. The validity of the genera with "uncoherent host range", such as Monsonella, Litomosoides and Cercopithifilaria, is confirmed and, consequently, their evolution by host-switchings. Dirofilaria and Onchocerca, types of two subfamilies, appear more closely related than with other onchocercids. Waltonellinae from anurans and Oswaldofilariinae from reptiles have a basal position. These filariae, and some others also considered primitive, do not harbour Wolbachia. Evidence for transversal transmission of the bacteria and a second acquisition event is given with the supergroup F, identified in Monsonella, in one of the Cercopithifilaria species and in arthropods.