We isolated porcine cytomegaloviruses (PCMVs) from lung samples of fattening pigs collected in the slaughter houses of 4 prefectures of Japan. Seven isolates were obtained and used for a comparison of serological characteristics by ELISA. J1, the first field isolate in Japan, and B6 which was isolated in the UK were also used in the study. The serological relationships between the isolates were analysed by the method of Archetti and Horsfall. OF1 showed serological differences with Chiba2 and Hiroshima. Differences were also observed between Chiba2 and ChibaC, ChibaC and Kagawa. B6 showed differences with OF2, Chiba3, ChibaC and Hiroshima.