The duikers from Makokou (Gabon) are parasitized by many species of Onchocerca but the adults are very often occult and can only be discovered by a systematical search. Three new species are described: O. sonini n.sp. in the feet-tendons, and O. lerouxi n.sp. in the muscular aponevrosis of the trunk of C. nigrifrons; O. beaveri n.sp. in the ligaments of the atlas-occipital articulation of C. monticola. Although their external appearance differs, these three species belong to a single group, which, from an evolutionary point of view, is intermediate between the more primitive Onchocerca of Equiids and those more evolved from other animals.