Hepatitis E virus is an enterically transmitted virus that causes endemic cases of acute hepatitis in many countries in Africa, and Southeast and Central Asia. Sporadic cases of acute hepatitis E also have been reported in developed countries. In non-endemic areas, most of the sporadic cases of hepatitis E are introduced from the endemic areas. Until now, only three cases of acute hepatitis E have been reported in Korea. Recently, we experienced nine cases of acute hepatitis, in which serologic studies showed positive of IgM anti-HEV. We report these as cases of acute hepatitis E. These cases suggest that HEV infection occurs sporadically in Korea and should be considered as a cause of cryptogenic acute hepatitis.