The authors carried out morphological examinations of lungs and heart in 20 days with prolonged hypoxia caused by surgical subglottic stenosis of the trachea by 50%. The studies showed that 30 and 60 days after the onset of hypoxia changes such as emphysema and chronic bronchitis developed in the lungs showing an increasing tendency, while in the myocardium microgranular disintegration and fatty infiltration of muscle fibres with simultaneous disappearance of glycogen was seen in the first period-after 30 days - while later, after 60 days fibrosis developed.