A cytopathic virus was isolated from the primary kidney cell cultures of apparently healthy guinea pigs reproduced in Mexico between 1982 and 1983. This virus produced intranuclear type A inclusion bodies in the infected cell cultures. Viral replication was inhibited by IUdR, indicating that the viral nucleic acid was DNA. The virus was sensitive to ether, chloroform and acid (pH 3.0), and passed readily through a 200 nm filter, but not through a 100 nm filter. Electron microscopy showed a spherical particle with envelope. These properties were consistent with those of Herpesviridae. In serologic survey of guinea pigs in Mexico and Japan, and of mice, hamsters, rats, rabbits, pigs, goats, horses and calves in Japan, neutralizing antibody against the isolate GPM 83-11 was detected in 4 of 46 infant guinea pigs about 3-4 weeks of age and in 9 of 30 breeding guinea pigs reproduced in Mexico, but neither in any of guinea pigs nor other animals in Japan.