We tested three new corneal preservation media in which the dextran in McCarey-Kaufman (M-K) medium was replaced by three preparations of chondroitin sulfate (CS): 1.5% CS, 5.0% CS, and 2.0% modified CS (K-Sol). One cornea from each of 36 pairs of corneas was placed in M-K medium and the opposite cornea was placed in one of the CS media. Endothelial preservation was evaluated by electron microscopy after storage at 4 degrees C for 1, 3, 5, 7, 10, and 14 days. We judged cellular preservation in a masked manner from the electron micrographs according to a morphologic grading system. Preservation in 1.5% CS solution was similar to that in M-K medium. Both 5.0% CS and K-Sol gave better endothelial preservation than M-K medium. The best preservation appeared to be in K-Sol, in which only 3% of the endothelial cells were disrupted after 14 days of storage at 4 degrees C.