The effects of extended preservation on transplanted corneas were investigated using McCarey-Kaufman (M-K) and K-Sol media. Cat corneas were preserved in either M-K or K-Sol at 4 degrees C for 5, 10, 15, or 20 days and were subsequently transplanted. Postoperatively, transplants were observed via slit-lamp biomicroscopy and pachymetry and at postmortem examination by light and scanning electron microscopy. In this study, we found no difference in the corneal graft clarity, thickness, endothelial cell count, or morphologic features of corneal transplants preserved in either M-K or K-Sol media. Storage for more than ten days in either M-K or K-Sol media led to primary graft failure. This study demonstrated equivalent results in corneal preservation using either M-K or K-Sol media. The development of better preservation media may require changes in essential nutrients rather than changes in osmotic constituents.