We radiotracked 23 Japanese dormice (Glirulus japonicus) in a natural oak forest and a larch plantation to locate their daily rest sites. In 363 tracking days, 123 rest sites were used, 72% in trees and 28% in shallow underground sites or a rock crevice. Nest boxes and tree cavities were the most frequently used rest sites in trees. Natural arboreal rest sites and nest boxes were used regularly by individual dormice, whereas most underground rest sites were used for only 1 day. Nest boxes and underground rest sites were used more frequently in the larch plantation than in the oak forest. Males used nest boxes more than underground rest sites, whereas females regularly used the same natural arboreal rest sites. Dormice had large home ranges relative to their body mass. Males had larger home ranges and moved for longer distances at night than did females. A close relationship between rest-site use and daily torpor was apparent; nesting material was not found in natural rest sites used only once, and dormice frequently changed their rest sites.