Seventeen children with vertically acquired hepatitis C virus (HCV) infection were followed from birth for a mean of 104 months. Alanine aminotransferase (ALT) levels were increased significantly at 3 and 6 months of age but were stable thereafter. HCV polymerase chain reaction was positive at 3 months in 16 patients and at 12 months in one patient. Viral load remained stable during follow-up at a mean value of 5.4 +/- 0.4 log10. Mild chronic hepatitis was the most common histopathological feature on liver biopsy, occurring in six of the seven children biopsied at a mean age of 4.0 +/- 2.4 years. Genotype did not seem to be related to the type of liver involvement. The results of this study suggest that vertically acquired HCV infection has a benign course in children, despite the presence of viraemia and persistent alterations in ALT levels.