Hepatitis C virus (HCV), the etiological agent responsible for the majority of cases of parenterally acquired liver disease, is found throughout the world. HCV is an enveloped virus with a small, single-stranded RNA genome. Because it uses an error-prone, RNA-dependent RNA polymerase, HCV has a high spontaneous mutation rate, and isolates of HCV display significant genetic heterogeneity. Isolates of HCV have been classified into at least six major genotypes and multiple subtypes based on sequencing and phylogenetic analysis (1 ). These genetic variants of HCV show a diverse geographical distribution. HCV types 1a, 1b, 2b, and 3a are the most prevalent in the US and western Europe (2 ,3 ), although all six major genotypes have been noted.