Patients with chronic obstructive lung disease may suffer from acute exacerbations of their disease, which may lead to acute respiratory failure necessitating endotracheal intubation and mechanical ventilation. We have compared retrospectively the results obtained with nasal positive pressure ventilation and those of standard medical therapy in acute relapses of severe COLD. The study showed that nasal IPPV (NIPPV) in control mode delivered for approximately 1 h, four times daily, six days a week over a 21 day period, does not result in independent improvement of acute exacerbation of COLD. In the next study the data seem to indicate, in apparent contrast, a marked reduction in the need for endotracheal intubation using noninvasive ventilation, both with assist-control and pressure support noninvasive modes, in comparison with an historical control group. We did not find a significant difference in the success rate of the two modes, but compliance to noninvasive ventilation was better with pressure support. In the former study patients showing neurological signs and requiring mechanical ventilation were excluded, while in the last study patients were selected on the basis of necessity of mechanical ventilation. The fact that in the last study, ventilation was applied by face mask instead of nasal mask may have influenced results. Further efforts are required to determine whether non-invasive ventilation is more a preventive measure to avoid endotracheal intubation, or is another means of delivering ventilatory support.