After revising several genera currently considered under the family Thornenematidae, they are now compared with other genera that have been regarded as closely related to them in the past. The morphological characters that have been used to characterize the genera and the family are critically reviewed. It is concluded that all genera belong to Dorylaimidae; that three genera, viz. Sicaguttur, Thornenema and Sclerolabia constitute the subfamily Thornenematinae under Dorylaimidae; that Opisthodorylaimus belongs under Mesodorylaiminae; and that the tax- onomic status of the genera Willinema, Lenonchium, Fuscheila and Silvallis has to be reassessed at subfamily level. © 1987, Brill. All rights reserved.