HCV genotyping by nucleic acid sequencing emphasizes the difficulties involved in carrying out a more precise determination of the infectant viral population, probably due in part to the finding of still unknown isolates. Signs of heterogeneity in the genotype composition of the viral quasi-species and its evolutionary dynamism over time, together with the role played by some, more potentially aggressive, isolates in causing hepatic damage, encourage a more in-depth study of such topics.