Nucleotide sequence analysis of hepatitis C virus (HCV) strains showed substantial variability leading to a classification into several genotypes and subtypes. The data correlating HCV genotypes and subtypes with hepatitis C viremia levels, demographic characteristics of patients (age, mode of transmission, duration of infection), and severity of liver disease are conflicting. The interpretation of several studies is further complicated because the molecular methods used lacked specificity for genotyping/subtyping and underestimated viremia levels, especially in patients infected with HCV genotypes 2 and 3. In the present study we investigated 97 consecutive patients with chronic hepatitis C using molecular "gold standard" methods. HCV subtyping was performed by sequence and phylogenetic analysis of the nonstructural (NS)-5 region and serum HCV-RNA concentration was assessed by a validated genotype-independent quantitative reverse-transcription-polymerase chain reaction assay using an internal RNA standard. Patients infected with subtypes HCV-1b, HCV-2a-c, and HCV-4 were older than patients infected with HCV-1a and HCV-3a. Serum HCV-RNA levels ranged from 1.5 x 10(4) to 1.0 x 10(8) copies/mL with no significant differences between median serum HCV-RNA concentrations in patients infected with different genotypes/subtypes. Although patients infected with HCV-1b were older, no biochemical or histological evidence was obtained that this subtype is associated with more severe liver disease. Furthermore, the present study showed a lack of correlation between the serum HCV-RNA concentration, biochemical parameters, and liver histology. The median serum HCV-RNA levels in patients with chronic persistent hepatitis, chronic active hepatitis, and liver cirrhosis were 5.0 x 10(6) copies/mL, 2.5 x 10(6) copies/mL, and 5.0 x 10(6) copies/mL, respectively. These differences were not significant. In conclusion, using optimized and validated molecular techniques, the present cross-sectional study showed no correlation between HCV genotypes/subtypes, viremia, liver function test results, and histology.