The virologic and histologic characteristics of congenital cytomegalovirus infection (CMV) were defined in 65 neonatal guinea pigs born from 27 mothers infected pregnancy. Infectious virus or tissue lesions were present in 54% of the neonates tested. Guinea pig CMV was detected most often in the salivary glands (72%) and spleen (33%) of infected guinea pigs. Less frequently, virus was also detected in the brain, lung, pancreas and liver. Tissue lesions were most frequently observed in the brain and kidney, but also occurred in the salivary glands, liver, pancreas, thymus and spleen. The histopathology was identical to that observed in infants with congenital CMV infection. Infectious virus and histopathology were present in newborn guinea pigs born from mothers infected at any time during gestation. Newborns from mothers infected during early stages of gestation and virus present most frequently in the salivary glands, whereas offspring of mothers infected in late pregnancy had virus present in several tissues. Acute maternal guinea pig CMV infection produced generalized CMV infection of the offspring which was followed by persistent infection in neonatal salivary glands. Lesions remained present in several neonatal tissues including the brain. The long term consequences of such lesions in affected guinea pigs remain to be determined. The results of the study emphasize the similarities between human congenital CMV infection and congenital guinea pig CMV infection, thereby underlining the utility of this animal model as a means of understanding human congenital CMV infection.