Although corneal transplantation is very successful for keratoconus and some other dystrophies, it is not nearly as successful for acquired corneal opacities. The usual cause of failure is allograft rejection. In high-risk cases a number of strategies are required to decrease the risk of rejection. These include suppression of inflammation, MHC matching, and local and systemic immunosuppression. For the results of corneal transplantation to improve, surgeons must be prepared to choose from a range of approaches, those best suited to the individual patient.