An epidemic of hepatitis B antigen (HB Ag)-positive viral hepatitis occurred in a large family and their acquaintances during a four-month period. Three adult members of the family had clinically apparent hepatitis and asymptomatic HB Ag-positive serum developed in the baby and grandmother. Two other family members were found to have antibody to hepatitis B. No one in the family but the index patient used illicit drugs parenterally but all had close contact with the index patient, the baby, and each other. This outbreak suggests means by which HB Ag may be transmitted by nonparenteral or inapparent parenteral routes in a family setting.