We transplanted 30 donor corneas preserved at 34 C for 15 to 33 days in culture medium containing 1.35% chondroitin sulfate and compared them with 30 corneas transplanted during the same period, but preserved only in McCarey-Kaufman medium at 4 C for one to 81 hours. Two months after keratoplasty there was no statistically significant difference in central endothelial cell loss between the organ-cultured grafts and those preserved in McCarey-Kaufman medium (9% vs 7% cell loss, respectively). The study detected with 90% power a difference in cell loss of approximately 10% or more. On the first postoperative day, the organ-cultured grafts were thicker than those grafts preserved in McCarey-Kaufman medium, and the thickest corneas were those cultured for the longest times. The corneal thickness was similar in the two groups after three weeks. These results demonstrated that donor corneal endothelial cells preserved for up to one month at 34 C in 1.35% chondroitin sulfate appear to survive and function after keratoplasty as well as those preserved at 4 C for one to three days in McCarey-Kaufman medium.