We report the results of nocturnal nasal-mask intermittent positive-pressure ventilation (NIPPV) for 12-24 months in a group of 29 patients with neuromuscular weakness or restrictive chest-wall or parenchymal defects. Seventeen patients demonstrated a statisticallly significant increase in PaO2, and decrease in PaCO2 with stable vital capacity after 1 year of such ventilation. Nine patients showed slight improvement in blood gas values and stable vital capacity at 1 year, but the changes were not significant. One patient was tested as NIPPV was begun, continues to use it for 2 hours per day, but has refused follow-up. One patient died after stopping ventilation himself, and a second whose deterioration could not be reversed or stayed died suddenly 18 months after beginning treatment. The 26 patients who responded to a questionnaire at 1 year believed that they were able to participate in more daily activities. Seventeen patients left the house at least three times a week, eight began to drive a car again, and six returned to work. We believe nasal-mask ventilation to be a safe and effective alternative to ventilation via tracheostomy in early chronic failure and to be effective in patients with restrictive defects resulting from chest-wall and parenchymal disease as well as neuromuscular weakness. Caution and careful supervision are necessary.