Conventional RNA extraction methods, such as SDS/phenol and AGPC methods involve time consuming and complicated manipulation procedures, which could be a cause of contamination. In this study, we compared the conventional methods with a method using a newly developed reagent, "SepaGene-RV" to extract RNA. The results obtained by the new method were the same as those obtained by the conventional methods in the comparative experiments with the sera of patients infected with HCV and detection limit tests using recombinant HCV genome. The sensitivity to detect HCV-RNA with SepaGene-RV was equivalent to that of conventionally used methods to extract RNA, and the manipulation procedure was simpler and it was less time consuming. In addition, we could detect plus-stranded and minus-stranded HCV-RNA by polymerase chain reaction assay (PCR) from liver tissue obtained from liver biopsy and peripheral blood mononuclear cells (PBMC). We confirmed that HCV infects not only liver tissue but also PBMC where replication occurs.