Preoperative risk factors that may influence the prognosis in penetrating keratoplasty were statistically analyzed on 698 consecutive eye that had been operated on at the University of Tokyo Hospital. A Cox multiple regression model (proportional hazards models) was constructed with simultaneous consideration of follow-up periods and prognostic factors. Six preoperative risk factors were identified: corneal endothelial damage, the presence of anterior synechiae, glaucoma, older donor age, the area of vascularization, and aphakia or pseudophakia. Simulations of the prognosis were attempted using the significant factors.