The incidence of influenza, parainfluenza, respiratory syncytial and adeno-virus antigens and morphological manifestations of acute respiratory viral infections (ARVI) in infants were studied on the materials of 188 autopsies of fetuses and newborns dying in the first 168 hours of life, i.e. in the perinatal period. ARVI were shown to be highly prevalent in the perinatal period. Morphological manifestations of infections increased with the duration of life: from minimal manifestations in stillborns to marked viral lesions in newborns of 3-5 days of life. Signs of ARVI were observed also in a number of cases of the so-called "noninfectious pneumopathies". A peculiar kind of necrotic pneumonias in newborns is described which are characterized by the complete lack of cellular reaction around foci of necrosis of the lung tissue.