In order to investigate a relationship between cellular DNA-content and enlargement in cell size of human corneal endothelium in healthy population, both nuclear DNA-cytofluorometry and cell morphometry were performed on individual cells of presumably normal corneas taken from six autopsy cases. The cornea was treated in 0.2 M phosphate buffer containing 60 mM Na2EDTA and fixed with absolute methanol. The endothelial-cell layer was separated from Descemet's membrane by placing the tissue in distilled water. The specimen was marked with rhodamine-labelled wheatgerm agglutinin (WGA)-lectin for identifying cell boundaries and subsequently stained with DAPI for measurement of DNA contents. The area of each cell was measured by means of a color image analyser and compared with its cytofluorometric nuclear DNA content. The enlarged endothelial cells which appeared with age contained diploid, polyploid or multiple nuclei. The polyploid and multinucleated cells had larger mean and maximum cell sizes and more irregular and polymorphous shapes than diploid cells. There were neither small polyploid nor small multinucleated cells. It was suggested that the loss of human corneal endothelium was compensated in vivo by cell size enlargement with or without doubling of nuclear DNA.