Structural manifestations of Herpesviridae infection, largely of herpes simplex, transmission and mode of entry were analysed and investigated by the authors on section material using light and immunofluorescent microscopy in combination with serological tests. In overall neonatal section material generalized herpetic infection was a frequent finding (4.7%). The lesions in type I and II herpes simplex were similar in manifestations. Structural evaluation of the viscera in prenatal and placental infections suggests affection of cells of epithelial origin with metamorphosis of the giant cells and a drastic increase of the nuclei exhibiting large inclusions rich in DNA. Alternative changes were more pronounced in the brain, while the destruction of the affected cells was more intensive in the lungs. Postnatal herpes simplex virus infection was also covered.