The effects of noninvasive positive pressure ventilation (NIPPV) in COPD patients (pts) with hypercapnic respiratory failure were evaluated. The study group consisted of 19 COPD pts (16M, 3F, mean age 60 +/- 8 years) on LTOT for at least 6 month before study. Patients were enrolled in random order to group I, which continued LTOT and to group II, which started nocturnal NIPPV and continued LTOT. There were 12 pts in group 1 and 7 pts in group II. Two pts from the group did not tolerate NIPPV and were transferred to group I. To ventilate the pts we used portable, volume ventilators. Mean time of follow-up in group I was 23 +/- 13 months and 16 +/- 10 months in group II. During that time died 5 pts from 1 and 4 pts from group II. Differences between functional variables (FEV1, FVC, FEV1/VC, PaO2, PaCO2, pH, PEmax, 6MWD), dyspnea, number of hospitalizations and mortality in both groups were not statistically significant. In both groups progression of the disease (decrease of FEV1, worsening of hypoxaemia and increase of hypercapnia) was observed. NIPPV did not slow down progression of the disease.