Objective:To investigate the familial clustering risk factors for hepatitis B in Shanghai area.Methods: A standard,two-page questionnaire was designed to investigate the risk factors for HBV infection in the family members of index cases.The risk factors were analyzed between families with HBV clustering and families without HBV clustering (controls).Results: A total of 870 family members from 298 families were investigated.Multivariable analysis showed that family members with liver cirrhosis (P=0.004,OR=2.548,95%CI 1.352-4.800) and sharing of towels (P=0.016,OR=1.864,95%CI 1.125-3.089) were the independent factors for familial clustering of hepatitis B.Conclusion: Family members with liver cirrhosis and sharing of towels are the major risk factors for intrafamilial transmission of HBV in Shanghai.