Previous classifications of the Nepticulidae were based on species from the northern hemisphere, primarily western Europe (including the United Kingdom) and North America. The revised classification presented in the present work was developed from a study of material primarily from southern Africa, but also from Australia, Europe, North America, and the Orient. Most of the descriptive section deals with the taxonomy of the Nepticulidae of southern Africa. Nevertheless, a guide to the supraspecific classification of the family was a major aim. Cladistic methods were used to assess genealogy as far as possible. The degree to which it has been elucidated is incorporated into the classification. As a result of the study, the Nepticulidae are divided into two subfamilies. One of these subfamilies is divided into two tribes. Fifteen genera and six subgenera are recognised. Two keys are presented, one to subfamilies and tribes and the other to genera and subgenera. The species from southern Africa are included in eight genera, three of which are new. One hundred and seventeen species from southern Africa are considered. Seventy- two new species are described in this work. Of these 40 have been published and 32 appear as manuscript names. For some species described by previous workers lectotypes have been designated where appropriate. The primary types of all the known species from southern Africa have been examined. Observations on adult structure are discussed from the viewpoint of phylogenetic relationships both within the Nepticulidae and between the family and other lepidopteran groups. This has led to a re-interpretation and expansion of some aspects of nepticulid morphology. Numerical phenetic methods, which include cluster analyses and an ordination technique (principal component analysis), were used to check my personal assessment of phena. The illustrations (phenograms and ordination diagrams) provide a visual summary of phenetic relationships of as wide a range of Nepticulidae as possible. Aspects of the nature of taxonomic characters, ancestor-descendant relationships, and homoplasy are discussed. Brief comments are made on distribution, and host-plant choice and phylogeny.