The respiratory disorders with various degrees of cardiac insufficiency were studied in 226 patients with acquired heart defects. The indices characterizing the external respiration, alveolar ventilation, alveolar-capillary diffusion, functional and real intrapulmonary shunts and acid-base state were followed up. The results from the numerous indices followed up significantly express the progressive intensification of respiratory disorders with the advancement of cardiac insufficiency. In stage I of cardiac insufficiency, prior to the manifestation of clinical signs of pulmonary stasis, distinct disturbances were established in DLCO, Qs/Qt, PaO2, which, to a great extent, characterize the early respiratory disorders and have a definite importance for the diagnostic and therapeutic behaviour. Most severe are the functional disorders in respiratory system in stage II B of cardiac insufficiency.