Immune reaction is the main cause for graft failure following penetrating keratoplasty. Endothelial immune reaction is the most frequent and most dangerous subtype of rejection because destruction of the graft endothelium can lead to graft failure. "Acute" endothelial rejection is treated by administration of topical and systemic steroids. Intracameral application of corticosteroids by means of an anterior chamber flush is an adjunctive measure that can stop the immune reaction immediately. This measure is thus recommended in all intermediate and severe endothelial rejections.