The correlation between response to antiviral therapy and pretreatment viral load in patients with chronic hepatitis C has prompted the development of quantitative assays to measure viral load. The aim of our study was to assess the clinical relevance of the newly developed semiautomated PCR system COBAS HCV MONITOR version 2.0 in comparison with (i) the AMPLICOR HCV MONITOR version 1.0 assay, which underestimates RNA concentration of hepatitis C virus (HCV) genotypes 2 to 6, and (ii) the QUANTIPLEX HCV RNA version 2.0 assay, which achieves equivalent quantification for each HCV genotype, with samples from 174 patients diagnosed with chronic hepatitis C before therapy. The level and range of quantification measured with AMPLICOR HCV MONITOR version 1.0 were 1 log lower than when measured with the COBAS HCV MONITOR version 2.0, at 0.261 × 10⁶ RNA copies/ml (range, 0.001 × 10⁶ to 2.50 × 10⁶ RNA copies/ml) and 4.032 × 10⁶ RNA copies/ml (range, 0.026 × 10⁶ to 72.6 × 10⁶ RNA copies/ml), respectively. The two assays showed a poor correlation (r² = 0.175). The level and range of quantification were similar when measured with the COBAS HCV MONITOR version 2.0 and QUANTIPLEX HCV RNA version 2.0 assays, at 3.03 × 10⁶ RNA copies/ml (range, 0.023 × 10⁶ to 72.6 × 10⁶ RNA copies/ml) and 4.91 Meq/ml (range, 0.200 to 49.5 Meq/ml), respectively. The two assays showed a strong correlation (r² = 0.686) for each HCV genotype. The duration of treatment (6 or 12 months) is modulated according to HCV genotype and viral load. Our results indicate that COBAS HCV MONITOR version 2.0 and QUANTIPLEX HCV RNA version 2.0 assays showing an equal dynamic range for each HCV genotype are suitable tools to assess patients before therapy.