We performed wide-field specular microscopy and pachymetry on 92 donor corneas to evaluate the changes occurring in the endothelium during moist chamber storage of up to 48 hours. Endothelial changes were quantitated with computer-assisted morphometry. The donor corneas were divided into two groups: younger (mean age, 34 years) and older (mean age, 72 years). No significant differences in endothelial cell density, coefficient of variation in cell area (polymegethism), percentage of hexagonal cells (pleomorphism), or central corneal thickness were noted between younger and older donors when storage intervals were similar. Within each group, while endothelial cell density remained constant, a marked increase in polymegethism and pleomorphism developed when storage was prolonged beyond 12 hours. Corneal thickness also increased, but there was no correlation between thickness and the extent of the endothelial changes. These results suggest that specular microscopy is a more reliable method of screening donor tissue than donor age or corneal thickness.