A 37-year-man with chronic hepatitis B was diagnosed as having antimicrosomal antibodies and subclinical hypothyroidism. The association of autoimmune manifestations with hepatitis B has been less frequently reported than with hepatitis C virus. It is discussed whether this patient illustrates a case of spontaneous development of antimicrosomal antibodies, only casually associated with the presence of hepatitis B virus, or there is a real causative relationship between both conditions.