The Ehlers-Danlos syndrome (or, as we shall attempt to emphasize here, the Ehlers-Danlos syndromes) is characterized mainly by changes in the joints and in the skin. The joint change is hyperextensibility, ie, loose-jointedness. The skin change is classically excessive stretchability, excessive bruisability, and excessive fragility. In the last ten years or so, many genetic disorders that in the past were considered to be a single entity have, on close scrutiny, been found to be a collection of two or more fundamentally distinct disorders. The Ehlers-Danlos syndrome is no exception to this experience. Today at least seven seemingly distinct forms of the Ehlers-Danlos syndrome can be recognized (Table), and this may well not exhaust the heterogeneity within this group. As with other categories of genetic disease, clinical features, genetic factors, and biochemical approaches have been used to distinguish the various forms. Of the three approaches, the biochemical one is the most