Acute posttransfusion hepatitis C was reported in a recipient of 3 units of red cells. The recipient became acutely icteric 6 weeks after transfusion, and HCV infection was diagnosed. Stored serum samples of the 3 implicated donations, which were negative with ELISA-2, were retested by PCR and 3rd-generation antibody tests. One implicated donation was PCR positive, but anti-HCV negative. Both other donations were negative in all tests. The donor was recalled to the Blood Bank 13 weeks after the implicated donation and was found to be ELISA-3 plus RIBA-3 positive. Eight months after the implicated donation, the donor is still PCR and RIBA-3 positive, whereas the recipient became PCR negative but remained anti-HCV RIBA-3 positive. The case shows that blood products from donors collected during the open window period of an HCV infection can transmit HCV to recipients.