The aim of the study was to estimate the sensitivity, specificity, positive (PPV) and negative (NPV) predictive values, and likelihood ratios for HCV-RNA PCR tests for the early diagnosis or exclusion of HCV infection in vertically exposed children. Data were included for children with confirmed HCV infection status from a European multi-center study. Confirmation was dependent on antibody status at or beyond 18 months, the ‘gold standard’ measure of infection status against which the use of qualitative HCV-RNA PCR tests was assessed. Of the 547 children included in this analysis, 193 were HCV-infected and 354 were not. Sensitivity of the HCV-RNA PCR test was low at birth (22%), but increased to 85% by 6 months. Specificity of RNA PCR was constant over age at 98%. The PPV of the PCR test rose from 33% at birth to 78% at 9 months of age, while NPV ranged from 96% to 99%. The high positive likelihood ratios from 1 month of age indicate strong evidence to diagnose infection but the negative likelihood ratios were consistent with weak evidence to exclude infection. The results suggest that the first qualitative HCV-RNA PCR test should be delayed until after the first month of life given the low sensitivity in the first few weeks. Although a negative test result after this time indicates probable absence of infection, this should be confirmed with a negative anti-HCV antibody test between 9 and 15 months of age as negative PCR results can be observed in infected children with fluctuations in viremia. J. Med. Virol. 78:305–310, 2006. © 2005 Wiley-Liss, inc.