The family Onchocercidae contains 78 genera, all of which are filarial parasites transmitted by blood-sucking vectors. The infective larval stages of 34 genera are described, including representatives of all those genera with large numbers of species and with the highest pathogenicity for man. A dichotomous key for the identification of infective larvae is presented, which may prove useful for epidemiological studies. Only the most easily recognized morphological characteristics have been taken into account. They appear to be of phylogenetic significance, for the correlation between these characters and the various genera currently recognized in the family Onchocercidae is good.