Autopsied cases (270) of influenza in children, reported the possibility of a hematogenic virus dissemination from the respiratory system. In the acute stage of the disease the antigen of influenza was revealed in the liver, intestine, kidneys, brain and other organs with adequate regularity. The antigen was localized in the epithelial cells and also endothelial, ependymal and some other cells. The latter were partly accompanied by specific structural changes similar to those that occur in the respiratory system in the presence of the same disease. Besides, degenerative, exudate and, now and then, proliferative and regenerative changes which were not specific for influenza, have been found in all affected organs. Of particular interest were the results of brain study, in which viral particles were revealed by EM examination in chronic inflammatory lesions. In the experimental study carried out on 180 newborn mice by means of histological, immunofluorescent, serological and virological methods, the possibility of generalization of influenza, and some aspects of the pathogenesis were studied and discussed.