Background: The Ehlers-Danlos syndrome is underclassified. Many patients with hyperextensibility of skin and joint hypermobility do not have diagnosis. Objective: To classify patients with clinical features of Ehlers-Danlos syndrome and to determine how many have the criteria. Patients and methods: In a retrospective study we selected patients with hyperextensibility of skin and joint hypermobility. There was a prospective phase in which we received new patients with the same diagnosis. We made a clinical hystory and a physical examination, and applied a questionnaire with the most important different clinical features from each subtype. In necessary cases we made a skin biopsy for hystopathological study, and when it was possible we performed an electron microscopy. Results: There were 64 patients, all of them with hyperextensibility of skin or joint hypermobility. Six patients were excluded because of the incomplete questionnaire. Twenty eight (48.3%) patients were classified as classical type, 8 as hypermobile type (13.8%), 9 as kyphoscoliosis (15.5%) and 4 as arthrochalasia (6.9%). Nine patients had no specific clinical features to classify them. There was no patient with vascular or dermatosparaxis types. Soft and velvety skin, repeated joint dislocations, multiples hernias, piezogenic papules, marphanoid habitus and the digestive tube bleeding were the clinical features with significant statistics. None of the hystopathological features or electron microscopy results had significant statistics. Conclusions: The Ehlers-Danlos syndromes are a clinically diverse group of similar disorders with a difficult diagnosis, which should be done by the clinical features. Because neither the hystopathology or the electron microscopy had shown specific characteristics of one subtype; it is of great importance to continue the genetic studies to classify correctly these patients. [ABSTRACT FROM AUTHOR]