for transplantation. Second, improved procurement techniques and storage media have further increased the number of corneas suitable for transplantation and have improved donor viability. Third, improvements in surgical instruments and technique, combined with improved microsurgical training of ophthalmologists and postoperative management have improved the prognosis for individual cases. As a result, more than 30,000 corneal transplants a year are being performed in the United States. Optimal characteristics of a donor cornea include adequacy of endothelial cell population and viability to ensure graft survival, and absence of potentially infectious agents to be transmitted to the recipient. Much attention has been paid to the transmission of infectious diseases by corneal transplantation. To date, only two viral diseases-rabies and CreutzfeldtJakob disease-have been documented to be transmitted by corneal transplantation." Recent investigators have isolated hepatitis B surface antigen from the washings of ocular tissue from corneal donors,4 while others have isolated the human immunodeficiency virus from corneal tissue.5-6 The importance of these observations is the possibility of transmitting a potentially fatal disease to the corneal transplant recipient. However, because isolation of these pathogens from donor material is