We antigenically and molecularly compared 5 parapoxvirus isolates and 7 viral DNA samples from clinical lesions of Japanese serows with 3 viruses from sheep and goats. All isolates from Japanese serows except one, Ishikawa-S, reacted with six monoclonal antibodies to orf virus (ORFV). Restriction endonuclease analysis using amplified viral DNA showed the ORFV-specific pattern in all samples except Ishikawa-S, which showed a bovine papular stomatitis virus (BPSV)-specific pattern. Partial nucleotide sequences of the envelope genes were determined and those of all samples from Japanese serows and sheep except Ishikawa-S were completely identical and also had high identities with the goat virus. These findings suggest that parapoxvirus infection in Japanese serows might be mainly caused by ORFV and accidentally by BPSV. The envelope gene sequenced here seems to be conserved in Japanese ORFVs.