Purpose. Endothelial cell loss can be observed after keratoplasty, therefore in a retrospective study we analysed whether there is a correlation between donor age,recipient age, time post-mortem, preoperative cell density, diagnosis of the recipient and post-operative endothelial cell density. Methods. The endothelial cell densities of 120 patients who had undergone penetrating keratoplasty were examined over a period of 2 years. We divided the patients into four groups based on the endothelial cell density over 2 years. We examined the groups with regard to the parameters given above. Results. The lowest postoperative cell densities 2 years after kerato plasty showed a high correlation with the highest donor and recipient age. Even the lowest preoperative cell density was found in this group. Patients who underwent keratoplasty because of keratoconus had the highest cell densities after 2 years and also the lowest donor and recipient age. The preoperative cell density was also highest in this group. Discussion. The results indicate a correlation between increasing donor and recipient age, decreasing preoperative cell density and loss of endothelial cells 2 years after penetrating keratoplasty. Patients with the diagnosis keratoconus should also receive transplants with higher donor age.