Nine cases (0.41%) of bacterial and fungal endophthalmitis developed out of a total of 2,210 consecutive penetrating keratoplasties performed between November 1983 and April 1989. Five of the nine cases (0.23%) had endophthalmitis related to donor tissue contamination. The donor tissue of these cases had a storage time of greater than 5 days. A retrospective analysis of 1,399 consecutive corneoscleral rim cultures showed a contamination rate of 29%. The most common organisms isolated were Propionibacterium 26%, diphtheroids 24%, Staphylococcus epidermidis 22%, and fungi 9%. There is a statistically significant increase (p less than 0.005) in the percentage of contaminated donor rims with a preservation time of more than five days. The risk of developing endophthalmitis is 12 times greater with a positive donor rim culture. Prolonged preservation of donor tissue can be a risk factor in developing endophthalmitis.