An orthotopic penetrating keratoplasty model was developed in the rat. An oversized (0.5 mm) graft was used and 8 interrupted sutures were applied. These sutures were not removed. Eleven grafts out of 13 were rejected by the 3rd week in the disparate group (Brown Norway rat to Lewis rat transplantation group), which was characterized by edema, opacity, and neovascularization. All grafts remained clear in the syngeneic group (Lewis rat to Lewis rat transplantation group). Immunohistochemical examination was performed. This model seems to be a reliable and reproducible one to evaluate rejection reaction in corneal transplantation.