It is recommended by the Eye Bank Association of American that the post-mortem time of donor tissue stored in intermediate storage should not exceed 6 h. In an experimental study we investigated the impact of post-mortem time on the storage of corneas kept in McCarey-Kaufman medium. Eyeballs of freshly slaughtered pigs were kept in moist chamber storage at 4 degrees C for 0, 6, 12, 24, and 48 h. Subsequently, corneal-scleral rims were dissected and stored in MK-Medium for 2 days at 4 degrees C. The corneas were stored in organ culture for another 2 days at 31 degrees C in MEM medium containing 10% fetal calf serum. A control group consisted of corneas that had been stored in organ culture for 2 days. Morphometric analysis revealed no significant changes in endothelial cell density compared to control corneas after up to 24 h of moist chamber storage prior to storage in MK medium. A significant decrease in endothelial cell density could only be detected in corneas that had been kept in moist chamber storage for 48 h before MK medium storage. We conclude that the recommendation that only donor corneas with short post-mortem times be used may exclude large amounts of potentially feasible tissue for penetrating keratoplasty.