Transplacental dissemination of herpes simplex has never been demonstrated, although one instance of congenital herpes infection has been described, which was followed by an unusually "benign" disease in the newborn. [SEE TABLE I IN SOURCE PDF] The present case report presents persuasive evidence that the disseminated fulminant form of the herpes simplex infection may begin before birth: (1) the suggestive maternal illness, (2) the unexplained fetal distress, (3) the delivery by caesarean section, without traverse of the genital tract, (4) the unusual placental lesions, characteristic of hematogenous dissemination of infection and histologically similar to the visceral lesions in the infected infant, and (5) the separation of the infant from the parents following delivery. However, intrauterine transmission was not proved unequivocally, since virus was not cultured from the placenta and only suggestive inclusion bodies were found in the placenta. It is possible that the virus entered the fetus via an ascending infection following rupture of the membranes, although this seems unlikely in view of the absence of pulmonary lesions, the short period between rupture of the membranes and delivery, and the presence and character of the villous placental lesions. The preservation and examination of placentas in suspected and proven cases of neonatal viral infection, and the study of maternal and fetal sera in these cases are valuable but neglected aids in diagnosing disease and elucidating its pathogenesis. Maternal history and/or physical examination in the immediate pre- or postpartum period are frequently abnormal. Such abnormalities should alert the physician to the possibility of disseminated herpes simplex infection in the severely ill neonate without demonstrable bacterial infection.