Dermatology and the human gene map. Chromosomal localization has been established for many genetic traits. Gene mapping may lead to the identification of disease genes, an understanding of pathogenesis, and the development of rational therapy, as well as facilitating antenatal diagnosis and genetic counselling. 'The new genetics' is therefore of great interest to the clinician. Unfortunately the complex technology and unfamiliar vocabulary of molecular biology often deter non-specialists from keeping abreast of these developments. This account explains the principles of gene mapping, discusses its relevance to dermatologists, and lists the established loci of dermatologically important genes. 