Complement fixation and virus neutralization tests confirmed that alphaherpesviruses isolated from free-living Apodemus flavicollis and Clethrionomys glareolus rodents form an antigenically identical or very close group. Immunofluorescence showed that antigen assembly and distribution within the infected cell resembles that of members of the Alphaherpesvirinae subfamily. Radoimmunoassay revealed close antigenic relatedness between 5 rodent herpesvirus isolates. This suggested a possible relatedness of these viruses to some virus species isolated from humans and animals.