Data were collected from 104 infected children who were followed up from birth for a mean of 49 (range, 6-153) months in 22 European centers, to outline the natural history of perinatal hepatitis C virus (HCV) infection. Fifty-four children were persistently HCV RNA positive, 44 were occasionally positive, and 6 never had detectable viremia. At least 90% of the children had evidence of ongoing infection at the latest analysis. Eighteen children became HCV RNA negative at their last assessments, but 40% of these had high alanine aminotransferase (ALT) concentrations. Infection was asymptomatic in all but 2 children, who developed hepatomegaly. Mean ALT concentrations decreased substantially after the first 2 years of life; 14 children had persistently normal ALT values. Signs of minimal to moderate inflammation were noted in all 20 patients who underwent liver biopsy. Perinatal HCV infection is usually asymptomatic in the first years of life, but the virus persists in most children, even in the absence of elevated ALT activity.