Twenty patients with severe and chronic respiratory insufficiency (SaO2 less than or equal to 80% - PaCO2 greater than or equal to 50 mmHg) were treated with intermittent ventilatory assistance. They used volumetric apparatus 2 to 8 hours a day, during at least 6 months (22 months +/- 13). Respiratory status never improved strikingly, on the contrary most of the time it worsened and patients needed other ventilatory technics and/or died (11 of 20). This technic of ventilatory assistance does not seem to really change the prognosis of these patients in a severe and chronic state.