BACKGROUND: To date there have been four instances of infection transmitted through blood transfusions derived from individuals who later developed variant Creutzfeldt-Jakob disease (vCJD). The identification of further transmission of vCJD through this route would have important implications for risk assessment and public health. STUDY DESIGN AND METHODS: Through the UK Transfusion Medicine Epidemiology Review (TMER) the fate of blood donations from individuals who develop vCJD is traced and recipients of labile components are identified. The details of recipients are cross-checked with the register of vCJD cases held at the National CJD Surveillance Unit (NCJDSU) to identify any linkage between donors and recipients. In the reverse study, when individuals with vCJD are found to have a history of blood transfusion the donors of the transfused blood components are traced and their details cross-checked with the vCJD register to identify any missed or unrecognized linkage between donors and recipients. CASE REPORT: A case of vCJD has been identified with a history of blood transfusion in infancy. The donors who provided the components transfused cannot be identified, but a blood donor known to have donated blood to another individual who subsequently developed vCJD could have been a donor to the index case. RESULTS: The at-risk donor is alive 20 years after the relevant donation and continued to donate for some years, until identified as at risk, with 27 other blood components issued for use in patients, none of whom are known to have developed vCJD. CONCLUSION: Circumstantial evidence has raised the possibility that the case in this report represents a further instance of transfusion transmission of vCJD. However, detailed investigation indicates that the pattern of events may have occurred by chance and disease in this individual may have been caused by transmission of bovine spongiform encephalopathy infection, as is the presumed cause in other primary cases of vCJD.