HCV is a heterogeneous virus that is classified by phylogenetic analysis into six genotypes, each with 1 or more subtypes; a seventh genotype was recently established, which is very rare and not expected to be encountered in clinical practice. Genotype 1 is the most prevalent in the U.S. population accounting for approximately three-fourths of isolates found. Historically, Genotype 2 and 3 infections have had better response relative to other genotypes to standard HCV treatment regimens based on pegylated interferon and ribavirin therapy. However, the development of new, direct-acting, anti-viral agents targeting the viral replication complex have resulted in significant response to treatment across all genotypes.  Currently, however, treatment protocol and duration recommendations are still based on genotype information.