101 pairs of human embryonic kidneys of 5–12 weeks’ gestation were maintained in whole organ culture by our previously described technique, with herpesvirus hominis types 1 and 2 added to our regular media. One kidney of each pair served as a control and was exposed to identical culture medium without virus. Cultures were maintained for 24–120 h to study the time sequence of viral infectivity. Organs were then examined for the presence of virus by electron microscopy and histochemical staining. Histological studies of virus-infected kidneys showed either (1) complete organ death or (2) virus localization in undifferentiated cells, plus disorganization of architecture in differentiated areas. Control organs showed normal organization.