We placed human donor corneas in M-K medium at 4 degrees C for 24 hours, cultured them in minimal essential medium at 34 degrees C for two to five weeks, and then either (1) placed the corneas in M-K medium at 4 degrees C for 48 hours before transplantation (Group 1, 47 eyes); (2) placed the corneas in M-K medium at 4 degrees C for 16 hours before transplantation (Group 2, 17 eyes); or (3) transplanted the corneas without postculture cooling to 4 degrees C (Group 3, 11 eyes). We compared the corneas preserved by organ culture with an equal number of corneas transplanted during the same period, but preserved only in M-K medium at 4 degrees C for one to four days. The central endothelial cell losses noted two months after keratoplasty were significantly greater in the organ-cultured corneas than in the M-K-preserved corneas in each of the three groups. The mean endothelial cell loss in the 11 organ-cultured corneas in Group 3 was significantly less than that in the 64 organ-cultured corneas in Groups 1 and 2. The corneas in Group 1 were also examined one year after keratoplasty, and the cell losses in the organ-cultured grafts remained significantly greater than those in the M-K-preserved grafts.(ABSTRACT TRUNCATED AT 250 WORDS)