Previously, in collaboration with Dr. Jin-Won Song, of the Korea University, we identified a novel hantavirus, designated Muju virus, in tissues of an arvicolid rodent, Eothenomys regulus, captured in Korea. The existence of other species of Eothenomys in Japan, as well as the Asian landmass, prompted us to search for Muju virus-related hantaviruses in Japan and Taiwan, in collaboration with Dr. Teruki Kadosaka of Aichi Medical University in Aichi, Japan, Dr. Chiharu Morita of Rakuno Gakuen University in Ebetsu, Japan, and Dr. Liang-Kong Lin of Tunghai University in Taichung, Taiwan; in addition, rodent tissues from arvicolid rodents (Clethrionomys rutilus and Microtus pennsylvanicus) have been obtained for study from Dr. Joseph Cook of the University of Alaska Museum in Fairbanks. Our attempts to amplify hantavirus sequences in tissues of a wide variety of arvicolid rodents, as well as murid rodents (such as Apodemus) and insectivores (such as Crocidura and Suncus), captured in Japan and Taiwan are summarized in Table 6. Puumala virus-related sequences were found in grey-sided voles (Clethrionomys rufocanus) captured in Ebetsu on Hokkaido, and these sequences showed greatest homology with hantavirus sequences amplified from animals captured in Sweden. Although we have hitherto been unable to detect hantaviral RNA in tissues of animals captured elsewhere, the existence of hantaviruses in such rodent and insectivore species is highly probable and further studies are warranted.