372 children with suspected liver disease were examined for serum HBsAg. Six (three boys, three girls) were found to be positive (1.6%). Further studies of these patients for up to three and a half years revealed elimination of HBsAg in one case only. Biopsies were performed in five patients. Three showed mild chronic hepatitis (two chronic persistent hepatitis, one unspecific reactive hepatitis). Chronic aggressive hepatitis was diagnosed in one patient. One child seemed to be normal on light microscopy, but the findings on electron microscopy were abnormal, the liver cell nuclei being filled with core particles. Two thirds of the family contacts of these children showed hepatitis B marker. Two pregnancies were observed in HBsAg-positive mothers. An infection of the babies was not demonstrable.