A great deal of controversy and concern exists over potential transmission of central nervous system diseases by corneal transplant. The purpose of this study was to evaluate the available data relative to this question, pertaining especially to transmission of infectious dementia. From these data, determination of conveyance risks are possible, and rational policies for donor inclusion criteria can be constructed. Retrospective analysis of available published data regarding transmission of infectious dementias was performed. Risk of disease transmission was calculated from population data. Of the various forms of dementia, only rabies, hepatitis B, and Creutzfeldt-Jakob disease (CJD) have been transmitted by corneal transplantation. Transmission of the first two viruses is preventable by serologic testing. Prevention of CJD transmission relies on clinical history. Despite the possibility of transmission and the lack of available testing, slow virus disease (CJD) has been transmitted only once. That this case represents an extremely rare event is supported by a lack of successful transmission via corneal transplant in monkeys; lower levels of infectious agent in cornea than in brain; lack of successful transmission of similar human dementias, including Alzheimer's disease to primates; the apparent requirement for homozygosity at codon 129 of chromosome 20 for transmission; lack of transmission in 5-10% of CJD cases even after brain inoculation; and low numerical risk of transmission based on population data. Only 0.5-4 CJD infected donors per year would be expected. Current Eye Bank Association of America criteria for donor exclusion based on suspicious history are adequate to protect against accidental conveyance of transmissible dementia.