BACKGROUND: Instead of hepatitis C virus (HCV) RNA test using RT-PCR, an enzyme immunoas-say for detection of HCV core protein as a simple, rapid method for the detection of HCV viremia has been developed recently. In this study, we investigated the usefulness of HCV core protein for the detection of HCV viremia by comparing the results of HCV RNA. METHODS: The study group included 71 patients; some of whom showed anti-HCV Ab. The HCV core protein assay was performed by enzyme immunoassay (Ortho Clinical Diagnostics, Raritan, NJ, USA). RESULTS: The concordance rate between HCV RNA and HCV core protein assay was 75%. Compared with the HCV RNA results, HCV core protein assay showed 50% sensitivity and 97% specificity. Among 17 patients whose results for HCV RNA were positive and those of HCV core protein were negative, all of them had anti-HCV Ab. CONCLUSIONS: Although the sensitivity of HCV core protein was not high in cases with anti-HCV Ab, the positive results for HCV core protein suggests the presence of HCV viremia. So, HCV core protein may be used as a simple and rapid method for detection of HCV viremia.