Hepatitis C virus (HCV) is believed to replicate via a viral-encoded, RNA-dependent RNA polymerase. This replication strategy has limited fidelity Thus, HCV is genetically heterogenous. To date, six HCV genotypes and more than 80 viral subtypes have been identified. Further, even within individually infected patients, HCV exists as a highly heterogenous population of closely related genome called quasispecies (1 –3 ). Viral quasispecies have been shown to have important pathobiological implications.