To identify correlations between the distribution of hepatitis C virus (HCV) genotypes and demographic, pathological and virological parameters of HCV-infected patients, we prospectively recruited 650 patients with biopsy-proven chronic hepatitis C without histological aspects of cirrhosis; none had been treated with antiviral therapy. Data regarding gender, age, mode of HCV transmission, alanine aminotransferase (ALT) and HCV RNA levels, immunoglobulin M (IgM) anticore values, liver histology and histological activity were obtained from each patient and correlated on multivariate analysis with infecting HCV genotype. Fifty-five per cent of the patients were infected with HCV genotype 1, 20% with HCV genotype 2, 18% with HCV genotype 3 and 7% with HCV genotype 4. Non-transfusional HCV transmission, low ALT levels, IgM anticore reactivity and a low histological grading score were independent variables associated with HCV genotype 1. Older age, female gender, post-transfusional transmission and a high histological grading score were related to HCV genotype 2, whilst younger age, history of current/previous drug abuse, high ALT values, low IgM anticore reactivity and high viraemic levels were associated with HCV genotype 3. History of illicit use of intravenous drugs and low HCV RNA levels were the only independent variables correlated with HCV genotype 4. Genotype 1 remains predominant in Italy but the prevalence of HCV genotypes is changing in relation to age and mode of transmission: Italian patients with HCV genotype 3 are younger and exhibit higher levels of ALT and HCV RNA than patients with other genotypes.