Transmission of donor disease to the corneal graft recipient appears to be a rare event. Nevertheless, the subject merits careful attention because of the broad spectrum of diseases these cases represent, the potential for transmission of other disorders, and the difficulties in diagnosis they pose. Infections, neoplastic diseases, and corneal disorders may be acquired by corneal transplantation. Very serious are viral infections, but only rabies, Creutzfeldt-Jakob disease, and hepatitis B have had documented transmission. Bacterial and fungal infections are a clear hazard to the graft. On rare occasions, the recipient has died. Although the transmission of local corneal disorders and dystrophies has yet to be documented, the potential seems clear, particularly with tissue from young donors where evidence for dystrophies, such as keratoconus and Fuchs' dystrophy, has yet to appear. Fortunately, in the United States, screening techniques appear to be largely effective in detecting donors who harbor diseases that are potentially transmittable.