On September 29, 2011, the United Network for Organ Sharing notified CDC of two patients who tested positive for hepatitis C virus (HCV) infection approximately 6 months after receiving kidney transplants from a deceased donor. Before transplantation, the donor had tested negative for HCV antibody by the organ procurement organization. Tissue also was procured from the donor for possible transplantation. The tissue bank performed an HCV antibody test on the donor's serum specimen that was negative and nucleic acid testing (NAT) that was positive, but misread as negative. Retesting of the donor specimen during the investigation confirmed the NAT results as positive. Donated tissue included 43 musculoskeletal grafts and one cardiopulmonary patch, which were distributed to health-care facilities in several states. An investigation was initiated to 1) identify potential sources of the donor's infection, 2) document the mode of transmission to the organ recipients, and 3) ensure timely notification of the implanting surgeons and testing of tissue recipients. Implantation of infected HCV tissue occurred after recognition of new HCV infection in the organ transplant recipients, highlighting the need for rapid communication between transplant centers, organ procurement organizations, tissue banks, and public health authorities regarding suspected transplantation transmission events.