The analysis of most important publications and the authors' own data on the pathological anatomy and pathogenesis of influenza are presented. Severe complicated forms of influenza are characterized by the development of acute bacterial tracheobronchites which are the source of staphylococcal aspirations into the lungs. The degree of severity of developing pneumonias is determined to a large extent by destructive changes in the lungs. The destruction of osmiophilic bodies in the alveolar epithelium and the disturbance of the surfactant system is conducive to pulmonary edema. An important role in the involvement of the lungs and other organs is played by viralstaphylococcal toxicity. Lymphoid-macrophage and leukocyte reactions responsible for the production of antibody, interferon, and other factors of resistance are very important for protection against influenza. During epidemics, particular attention should be paid to combinations of influenza with cardio-vascular diseases.