There is little information on the clinical course of transplantation from HCV-positive donors. However, it seems that there is no increased risk of acute liver failure after the procedure and that the presence of HCV-RNA in serum is necessary for transmission to take place. We report a case of allogeneic CD34-selected peripheral stem cell transplantation from an HCV-infected donor with viremia with a special clinical and virological course. After the selection procedure and cell washing we could not detect HCV-RNA by PCR in the wash buffer, but HCV-RNA was positive by PCR in the selected cells. Once the patient received the transfusion of the selected product HCV was detected in the PBMCs and at very low concentration in serum. HCV was also demonstrated in the hepatocytes with the in situ hybridization technique. In conclusion, we have shown that CD34+ cell selection from an HCV-positive allogeneic donor does not prevent HCV infection in the recipient. Our results also suggest that HCV replicates in PBMCs in vivo and that these cells release viral particles that can infect the liver.