Viral RNAs are detected commonly in serum by hybridization and polymerase chain reaction (PCR) methods for both clinical and research purposes. Two methods of extracting viral RNA were evaluated prior to amplification by PCR. One was a conventional phenol-chloroform method and the other used a standardized, manufactured kit. The efficiency of extraction was tested by semi-quantitative amplification of hepatitis C viral and GB virus-C/hepatitis G viral RNAs. The standarized commercial method, although more time efficient, resulted in an approximately ten fold less sensitivity. Thus, in situations where maximum sensitivity is needed, the more labor intenstive phenol choloroform method is recommended.