Nucleic Acid Testing (NAT) is currently not required for solid organ donors screening. It was reported that a persistent HCV viremia in the absence of anti-HCV antibodies detectable by the contemporary screening assays do exist (MMWR 2003, Apr 4;52(13), Transfusion, 2003, Jul;43(7)). The prevalence of such a pattern is unknown among organ donors. Determining the frequency of transplantations from such donors and the risk for transmitting HCV to recipients is important in evaluating whether additional prevention measures are warranted. The aim is to estimate the frequency of HCV viremia among anti-HCV antibody negative organ donors in a large transplantation center. We tested 575 donors available for organ donations between 10/2002 and 11/2003. All specimens were tested for anti-HCV by 2 HCV EIAs (Abbott Laboratories, Chicago and Ortho Diagnostics, Raritan NJ) and for HCV RNA using Transcription-Mediated Amplification TMA assay (VERSANT, Bayer Diagnostics, Tarrytown, N.Y.). Anti-HCV negative HCV RNA positive specimens were re-tested for HCV RNA and anti-HCV using another aliquot from the same donor. Among 575 donors with specimen available for testing, 34 were repeatable anti-HCV reactive, and 33 were HCV RNA positive (Table). Six donors were repeatedly HCV RNA positive (TMA signal strength 451,751 - 1,244,796) in the absence of anti-HCV antibodies. For 4 donors we quantified their HCV viremia using bDNA and quantitative TMA assays (in house qualitative TMA, Bayer Diagnostics, and Berkeley, CA). Their HCV viral load ranged from 50 to 22,250 copies/ml and their genotypes were 2b (n=1), 3a (n=1), and 1 (n=3). One donor had HCV RNA too low for genotyping (LIPA, Bayer Diagnostics, and Tarrytown, N.Y.). We found that 1% of prospective organ donors were HCV RNA positive in the absence of detectable anti-HCV antibodies. Such a frequency is higher than those reported for blood donors and most likely reflects differences in pre-testing screening and epidemiology of blood versus organ donor populations. Our data suggests that NAT may contribute to the reduction of HCV transmission in the transplantation setting.