Members of the dystrophin family of proteins perform a critical but incompletely characterized role in the maintenance of membrane-associated complexes at points of intercellular contact in many vertebrate cell types. They interact with, amongst others, the transmembrane laminin receptor dystroglycan, cytoskeletal actin and, indirectly, the intracellular membrane-associated signalling enzyme neuronal nitric oxide synthase (nNOS). Here we describe sequences of a range of dystrophin-related proteins from vertebrate and invertebrate animals (including the important model organism Drosophila melanogaster ) and infer an evolutionary history of this family and its relationship to the distantly related dystrobrevins. It appears that most metazoa possess sequences encoding a single highly conserved dystrophin-like protein in addition to a presumed distinct dystrobrevin, derived from an early duplication of an ancestral gene. In the vertebrates (but not the protochordate Amphioxus), the single invertebrate dystrophin-like gene has undergone serial duplication to generate at least three distinct genes encoding proteins which have adopted specialized roles. It is hoped that this broadening of the biology of the dystrophins will afford further opportunities for the advancement of our understanding of the fundamental defect underlying the variety of human genetic disorders which result from aberrant or absent dystrophin-associated complexes.