A total of 69 small mammals of 6 species were collected in localities Marcelová and Kopác (southwestern Slovakia) and investigated. Two strains of murine herpesvirus (MHV) have been isolated and reisolated from Apodemus flavicollis. Both virus strains killed suckling mice after i.c. and i.p. inoculation. Adult mice were killed 4-7 days after i.c. inoculation. Cross antigenic reactions among 14C aminoacid hydrolysate labelled MHV-72 infected Vero cells and mouse immune sera against the two new isolates and rabbit immune sera raised against purified MHV strains No. 72 and No. 76 were done. Profiles of immunoprecipitated proteins are almost identical. All used immune sera crossreacted with major proteins of MHV-72 strain. We conclude that the two virus isolates from Apodemus flavicollis are new strains of MHV.