BACKGROUND: Variant Creutzfeldt-Jakob disease (vCJD) is a novel human prion disease caused by infection with the agent of bovine spongiform encephalopathy (BSE). Epidemiological evidence does not suggest that sporadic CJD is transmitted from person to person via blood transfusion, but this evidence may not apply to vCJD. We aimed to identify whether vCJD is transmissible through blood transfusion. METHODS: The national CJD surveillance unit reported all cases of probable or definite vCJD to the UK blood services, which searched for donation records at blood centres and hospitals. Information on named recipients and donors was provided to the surveillance unit to establish if any matches existed between recipients or donors and the database of cases of vCJD. Recipients were also flagged at the UK Office of National Statistics to establish date and cause of death. FINDINGS: 48 individuals were identified as having received a labile blood component from a total of 15 donors who later became vCJD cases and appeared on the surveillance unit's register. One of these recipients was identified as developing symptoms of vCJD 6.5 years after receiving a transfusion of red cells donated by an individual 3.5 years before the donor developed symptoms of vCJD. INTERPRETATION: Our findings raise the possibility that this infection was transfusion transmitted. Infection in the recipient could have been due to past dietary exposure to the BSE agent. However, the age of the patient was well beyond that of most vCJD cases, and the chance of observing a case of vCJD in a recipient in the absence of transfusion transmitted infection is about 1 in 15000 to 1 in 30000.