SummaryThe National Institute for Insurance of Disease and Disablement (RIZIV/INAMI) in Belgium reimburses the costs of long term oxygen therapy (LTOT) by concentrators since 1984 and by liquid oxygen since 1988 for specific categories of patients supervised by approved medical centers. Since then we prescribed these therapies for 83 patients (49 with COPD, 12 with lung fibrosis, 22 with miscellaneous diseases). Since 1984 40 concentrators were prescribed of which 34 have been installed and 11 were still operating in July 1992 at the end of the study: 12 patients died, 2 stopped LTOT and 10 switched to liquid oxygen. Since 1989 43 patients started with liquid oxygen systems, together with the 10 patients who switched from concentrators to liquid oxygen, thus S3 liquid oxygen systems had been described and 46 were still in use in July 1992: 5 patients died and 2 stopped LTOT patient characteristics at entry were: age 62±11 years (mcanilSD), Pa0250±6 mmHg, PaC0247±10 mmHg, polycythemia in 12%, clinical right heart failure in 47% and ECG signs of right ventricle hypertrophy in 70%. Two year survival was 75% for the whole group and 60% for the COPD patients. In patients with COPD improvement of Pa02 (on air) after 1 year of LTOT (+10±8 mmHg in survivors versus 0±6 mmHg in non-survivors) was significantly related to survival (p<0.05). Significant differences between the first