Ten excised rabbit corneas were bathed posteriorly with glutathione bicarbonate Ringers solution (GBR), while anteriorly the bathing solution was either GBR or sodium chloride solution (NaCl). All solutions had an osmolarity of 305 +/- 2 mOsm/kg. The corneas were fixed after 150 min exposure to the solutions, and prepared for electron microscopy. Morphometric analysis of the electron micrographs was conducted by an observer unaware of the anterior bathing solution. In each case, the epithelium was examined along a 1500 micron stretch of the basement membrane. Cells were categorized as normal, abnormal, and sloughing. Abnormal cells showed cytoplasmic and nuclear pallor, and disrupted cell membranes. Sloughing cells showed partial separation from the underlying epithelium. Corneas exposed to NaCl showed statistically significant differences from those exposed to GBR; the differences occurred in both the number of abnormal cells, and the number of sloughing cells. All observed ultrastructural changes were limited to the surface region of the epithelium. It is concluded that sodium chloride solution is inadequate at maintaining the epithelial surface.