An 81-year-old Japanese womanvisited our hospital because of abdominal discomfort. Physical examination revealed that she had an abdominal mass. A combination of ultrasonography, computed tomography, magnetic resonance imaging (MRI), and hepatic asialoglycoprotein scintigraphy was utilized to make a diagnosis. Wefound that she had a downward elongated hepatic lobe or Riedel's lobe which did not appear to be commonin our district. The prevalence of Riedel's lobe in the Asian population has not been studied. Furthermore, this is the first report that describes the MRIand hepatic asialoglycoprotein scintigraphy features of Riedel's lobe of the liver. (Internal Medicine 39: 136-138, 2000)