Age-related changes in corneal endothelial cell size were investigated in 116 eyes, from newborn to 96 years of age, by light microscopy. The preliminary findings show a regional distribution of cell changes on the endothelial surface. The endothelium of a newborn was homogeneous in cell size and shape. From the third decade of life onward, polymorphism and cell size variations occurred in the central endothelium. In corneas of patients over 50 years old, one-third of the cases often had a geographic arrangement of cells of increased size in the mid-periphery (3.5-4.0 mm paracentrally). Small cells were always predominant at the periphery.