This paper is chiefly aimed at reassessing the limits of four bombycoid families, namely the Eupterotidae, Saturniidae, Lemoniidae, and Brahmaeidae. An incompletely resolved cladogram is proposed for the whole 'bombycoid complex' (Mimallonoidea + Lasiocampoidea + Bombycoidea). Within the Bombycoidea, the primary dichotomy is considered to lie between the Eupterotidae + Bombycidae s.lat. + Endromidae + Mirinidae + Saturniidae, and the Carthaeidae + Lemoniidae + Brahmaeidae + Sphingidae. Sharing at least nine synapomorphies, the Lemoniidae and Brahmaeidae are regarded as reliable sister groups, and the Lemoniidae + Brahmaeidae are proposed as a sister group to the Sphingidae. Another newly proposed clade groups together the Endromidae, Mirinidae and Saturniidae. At family level, the Hibrildidae are synonymized with the Eupterotidae (syn. n.), for which the most significant autapomorphy lies in a previously unnoticed particularity of the female hind leg (distitarsus typically provided with a midventral row of spines). Sexual dimorphism in leg structure also leads to a redefinition of the Saturniidae, a family which must include, with subfamily rank (stat. rev.), the 'Oxytenidae' and 'Cercophanidae' of modern authors. A pair of distal, tooth-like structures on the fourth tarsomere of the female fore leg can thus be ascribed to the ground plan of the Saturniidae, along with a few other convincing autapomorphies. On the other hand, the 'Apatelodidae' are only tentatively placed in the 'Bombycidae sensu lato', a group provisionally resurrected insofar as the Apatelodidae sensu auct. prove to be diphyletic. As a matter of fact, the 'apatelodid' subfamily Epiinae is synonymized with the Bombycinae (syn. n.) in consideration of a rather large number of synapomorphies. When more extensively studied, the morphology of the eighth sternum of the male abdomen might lead to a slightly different, more restricted, concept of the Bombycidae (Le. excluding 'true' Apatelodidae). Often regarded as incertae sedis, the African genera Sabalia Walker and Spiramiopsis Hampson are definitely assigned to the Lemoniidae and Brahmaeidae respectively. Autapomorphies of these two families are recorded and discussed, as are those found to characterize the Sphingidae. Three subfamilies are tentatively recognized within the latter (Smerinthinae stat. rev., Sphinginae, Macroglossinae), five within the Eupterotidae (Hibrildinae, Tissanginae, Janinae, Panacelinae, Eupterotinae), and four within the Bombycidae s.lat. (Apatelodinae, Phiditiinae subfam. n., Prismostictinae [= Oberthueriinae, syn. rev.], Bombycinae). Three of these subfamilies are considered in a new sense, viz. the Panacelinae, Apatelodinae, and Bombycinae. Although the phylogeny of the Saturniidae is not fully taken into account in the present study, the composition of three saturniid subfamilies is critically examined (Oxyteninae, Cercophaninae, Ludiinae), and the Oxyteninae are viewed as the most 'primitive' member of the family.