We examined a father and son affected by Ehlers-Danlos syndrome type II. Both patients had micrognathia together with ligament and skin hyperlaxity. The son exhibited complete cleft palate. Ultrastructural studies revealed abnormal collagen fibrils in the dermis of both patients. In the child the most striking alterations consisted of lateral fusion of an enormous number of collagen fibrils giving rise to huge polymorphic collagen masses. In the father's dermis the great majority of collagen fibrils appeared normal; however, lateral fusion of fibrils together with local abnormal collagen aggregation were occasionally seen. In both patients the dermal elastic network was well developed and elastic fibers appeared normal.