A case of fulminant viral hepatitis type B in the late stage of pregnancy was successfully treated with glucagon-insulin therapy, corticosteroids and other drugs. A 26-year-old female (housewife and primipara) suddenly developed severe hepatic dysfunction and disturbance of consciousness at the 36th week of pregnancy. Sequential blood examinations revealed early response to HBs antibody and delayed response to HBc antibody but HBs antigen was not detectable. The two antibodies disappeared from the serum rapidly and anti-HBc IgM remained undetectable throughout the clinical course of the acute hepatitis. It is not rare for HBs antibody to appear and for HBs antigen to disappear rapidly in the early stage of the clinical course of fulminant viral hepatitis type B. Anti-HBc IgM is considered valuable in the diagnosis of viral hepatitis type B. However, the present case demonstrated that anti-HBc IgM may be undetectable throughout the clinical course in some cases of viral hepatitis type B.