The giant cells forming the Elschnig pearl mass after extracapsular cataract extraction are derived from lens epithelium. They are interconnected by gap-junction and desmosome-like structures. They stain homogenously and show few organelles. Active autolysis was demonstrated in some regions. The ultrastructural features of the giant cells in this type of secondary cataract share many of the characteristics of fiber cells. Because of profound changes in the environment postoperatively, these cells have developed other shapes and characteristics than normal lens fiber cells.