After a brief recall of etiology and anatomo-pathology, the authors tried to sum up the knowledge concerning the physio-pathology of kyphoscolioses. First the respiratory repercussion of the disease was studied with its classical spirometric data, the abnormalities of gas exchanges (alveolar hypoventilation, decreased diffusion capacity, inhomogeneous distribution of the ratio ventilation/perfusion which plays a large part in these abnormalities), altered ventilatory mechanics and the response to CO2. Then they studied the anatomical and functional repercussion on the lesser circulation which is at the origin of the chronic pulmonary heart. When present, correlations with the clinic are underlined. In a second part, the clinical evolution of the respiratory insufficiency in kyphoscolioses is approached. The brutality of respiratory decompensations and the very poor prognosis linked to the beginning of a chronic pulmonary heart are underlined. Finally, the therapeutical side of the disease is approached. The classical medical and surgical means are recalled and the paper ends on the changing of the prognosis, which became possible because of the techniques of ventilation at home, currently in expansion.