Corneal transplantation is the most widely practiced form of clinical transplantation. This was made possible by the development of donor handling and preservation techniques, such as cooled culture media and organ-culture systems, that guarantee a sufficient supply of donor tissue. Corneal grafting is performed to improve visual function, to preserve the integrity of the eye, or to reduce pain. Patients with visual disability who present with keratoconus or dystrophy have a good prognosis for retaining a thin, transparent graft on a long-term basis. In this patient group the limiting factor for a gratifying visual outcome is high residual postkeratoplasty astigmatism, a still-too-frequent occurrence. Refinement in trephination techniques should help overcome this pitfall. Patients with vascularization or regrafting who are in the high-risk category may benefit from HLA matching or the use of cyclosporine and other immunosuppressive agents that are currently being tested in experimental models for reducing the impact of allograft rejection.