Polarization optical methods were used for the study of the submicroscopical structure of the cell membrane of the corneal and scleral fibrocytes and of the corneal endothelial cells. The bimolecular lipid layers of these cell membranes are similar. They show a loose structure and are mainly composed of phospholipids with unsaturated hydrocarbon chains. The protein-mucopolysaccharide layers of these membranes are studied by . A char-Topo-optical reaction acteristic structural difference was found between the fibrocytes of the cornea and these of the sclera. The cell membrane of the corneal fibrocytes has a rich acid mucopolysaccharide content, mainly sulphated acid mucopolysaccharides, whereas the cell membrane of the scleral fibrocytes has a lower acid mucopolysaccharide content, the sulphated acid mucopolysaccharides being absent. The protein-polysaccharide layers of the fibrocytes show a similar structure as their own intercellular substance. The basal cell membrane of the corneal endothelial cells are similar to the cell membrane of the corneal fibrocytes, while the apical cell membranes show a very low acid mucopolysaccharide content.