The genus Anonchus is revised. The genera Assia and Haconnus are considered to be synonymous with Anonchus on the basis of the morphological analysis. Additional descriptions of six species, viz. A. maculatus, A. mirabilis, A. millelacunatus, A. palaeotropicus, A. coomansi and A. pulcher are provided on the basis of type material or recently collected populations. The lectotype of A. monohystera is designated and described and the synonymy of this species with A. maculatus is confirmed. Two new species are described; A. winiszewskae sp. n. from Paraguay and A. venezolanus sp. n. from Venezuela. Several aspects of the morphology are described and the variability and diagnostic significance of the main morphological characters discussed. A study of intrageneric and suprageneric taxonomy of the genus Anonchus is presented. The subfamily Aphanolaiminae is reinstated for the genera Aphanolaimus, Aphanonchus and Paraphanolaimus and raised to family rank. The family Aphanolaimidae includes two subfamilies: Aphanolaiminae and Anonchinae. An emended diagnosis and a revised classification of Anonchus are proposed and a key to the species of the genus is provided.