Six patients with chronic respiratory failure associated with hypercapnia were treated with nasal intermittent positive pressure ventilation (NIPPV) at home. NIPPV was delivered via a custom molded nasal interface described by McDermott. The patients consisted of one patient with kyphoscoliosis, three with Tb-sequela, one with COPD, and one with neuromuscular disease. Each patient had been treated with oxygen therapy until assisted ventilation was initiated because of CO2 retention. NIPPV was administered using a volume cycled flow generator set to deliver a minute volume such that PaCO2 was maintained between 35 and 45 Torr on NIPPV trial performed during wakefulness under the condition of no leakage from the mask. Supplementary oxygen was added so that oxygen saturation was maintained above 90 percent during more than 95% of nighttime NIPPV. Arterial blood gas tensions during daytime spontaneous breathing showed an improvement (PaCO2 68.3 +/- 7.2 Torr, PaO2 70.4 +/- 15.5 Torr, SaO2 91.6 +/- 4.3% before treatment; PaCO2 55.8 +/- 4.7 Torr, PaO2 87.5 +/- 16.5 Torr, SaO2 95.5 +/- 1.7% on treatment, mean +/- SD). The duration of NIPPV at home ranged from 2 to 24 months (11.7 +/- 6.8), and there was no hospitalization due to exacerbation during this period. In conclusion, NIPPV via a custom molded mask is simple, noninvasive, and suitable for the provision of long-term and domiciliary assisted ventilation.