We evaluated retrospectively the short-term and the long-term prognosis of 105 patients with COPD and prolonged respiratory insufficiency admitted to our respiratory intensive care unit from 1976 to 1980 for acute respiratory failure. All subjects underwent intermittent negative pressure ventilation by means of an iron lung to overcome the acute episode. Twelve patients died during hospitalization, six were lost after discharge, while 87 were successfully weaned and were included in a follow-up lasting five years. All relapses of ARF were treated by INPV. The survival rates after one and five years were 82 percent and 37 percent, respectively and were significantly influenced by factors such as age, chronic cor pulmonale, FEV1/VC, PaCO2 on admission. The survival rate observed in our patients was better than that reported previously by other authors in COPD patients with ARF submitted to mechanical ventilation after intubation. These results suggest that INPV can improve survival in this category of patients, but a controlled clinical trial will be needed to address this issue.