In vitro cultured skin fibroblasts derived from Ehlers-Danlos Syndrome (EDS) type I to VIII patients lack fibronectin-containing extracellular matrix (FN-ECM) which can be restored when EDS cells are cocultivated over a feeder of control fibroblasts. Further analysis, focused on EDS types III and IV cells, showed that partial matrix correction in EDS type III cells can be obtained by their cultivation over a feeder of EDS type IV fibroblasts, but not vice versa. An apparently normal FN-ECM can be restored in EDS types III and IV cells also by the addition of cellular--but not plasma--FN. These biological features might be used for a better understanding of ECM assembly and for the characterization of the different EDS cell types.