A previous study in the Liverpool district on patients receiving long term oxygen treatment using a domiciliary oxygen concentrator showed that only 55% were both using oxygen therapy correctly and had stopped smoking. To try and identify which factors influence patient behaviour, all 55 patients in this district receiving long-term oxygen therapy for hypoxaemic chronic airflow limitation were studied. We found that those with more symptoms were more likely to comply with this therapy. The prescription of a concentrator on the advice of a hospital physician did not improve on the compliance rates attained in those patients assessed by the general practitioner alone.