The Ditrysia, which comprise the great majority of extant Lepidoptera, are divided into thirty superfamilies (instead of the fifteen to twenty usually recognized). Several of them are conceived in a new sense and one is newly proposed: the Choreutoidea. The Dudgeoneidae are reassigned to the Cossoidea, the Sematuridae and Uraniidae to the Geometroidea, while the Anthelidae and Lasiocampidae are placed in the Lasiocampoidea, a superfamily differing from the Bombycoidea mainly in retaining unfused prothoracic coxae in the larva. The Alucitoidea comprise the Tineodidae, Oxychirotidae and Alucitidae, and the Drepanoidea the Epicopeiidae and Drepanidae. Sister group relationships are recognized between the following superfamilies: Yponomeutoidea / Gelechioidea, Cossoidea / Sesioidea, Alucitoidea / Pterophoroidea, Hesperioidea / Papilionoidea and Drepanoidea / Geometroidea. Reliable monophyletic groups are the Mimallonoidea + Lasiocampoidea + Bombycoidea and the Hedyloidea + Rhopalocera. A few clades are suggested at a higher level, e.g. the Apoditrysia, the Obtectomera (based on two autapomorphies: pupa with fixed abdominal segments 1-4, and imago with modified pulvilli) and the Macrolepidoptera (mainly based on the shape of the first axillary sclerite in the forewing base). Several other changes are introduced: the ' Pseudocossinae' are restricted to the Madagascan genus Pseudocossus Kenrick (possibly belonging in the Brachodidae); the Macropiratinae (stat. n.) are regarded as the most primitive Pterophoridae; the Charideinae are transferred from the Zygaenidae to the Thyrididae; within the Thyrididae, the Argyrotypinae are regarded identical with the Siculodinae (syn. n.). Finally, two families are newly proposed within the Apoditrysia: the Simaethistidae (fam. n.) and Whalleyanidae (fam. n.). The superfamily relationships of these two families have not been determined.