Following a longitudinal study of chronic non-A, non-B hepatitis in Italy and Spain, we evaluated the epidemiologic and clinical features of chronic hepatitis C in 77 consecutively observed children (35 male; mean age, 4 years) without underlying systemic diseases. All subjects were positive for antibody to hepatitis C virus in serum by second-generation tests. Forty-six patients had received blood transfusions in the perinatal period; 12 had a mother with antibodies to HCV in serum (five of these mothers were drug users or partners of a drug user); seven had a history of putative percutaneous exposure; and 12 had not been exposed to any risk factors for viral hepatitis. At presentation, only 22% were symptomatic, mean alanine-aminotransferase levels were three times the upper normal value, and liver histology showed active disease in only nine of 28 cases (32%). During a mean observation period of 6 years, only 11 of 57 patients (19%) complained of symptoms and 11 of 40 cases (27%) had histologic features of active hepatitis. Two patients had severe hepatitis with associated cirrhosis. However, only six of 57 cases (10%) achieved sustained biochemical remission. The clinical features and the outcome were similar in both the posttransfusion and the community-acquired cases. These results indicate that transfusions in the perinatal period are the single most important cause of hepatitis C in otherwise healthy children. Community-acquired cases represent an heterogeneous epidemiologic group in which maternal transmission, whether perinatal or postnatal, could be relevant.(ABSTRACT TRUNCATED AT 250 WORDS)