OBJECTIVES: The aim of the study was to assess the extent and quality of follow-up of patients on LTOT. SETTING: The Danish Oxygen Register. SUBJECTS: A total of 890 chronic obstructive pulmonary disease (COPD) patients who were on long-term oxygen therapy (LTOT) during the period from 1 November 1994 to 31 August 1995. MAIN OUTCOME MEASURES: The extent and quality of follow-up. RESULTS: Only 38.5% of the patients were followed up in the study period, and only 17.5% had a 'sufficient follow-up' defined as at least one follow-up visit within 10 months which included measurement of arterial blood gases or pulsoximetry with oxygen supply, verification that the patient used oxygen > or =15 h day-1 and was nonsmoker. Female gender, LTOT initiated 3-12 months ago, LTOT started by a chest physician at pulmonary department and LTOT prescribed > or =15 h day-1 were found to be significant predictors of 'sufficient follow-up' (odds ratio (OR): 1.7, 2.0, 3.7 and 1.9, respectively). CONCLUSIONS: The extent and the quality of follow-up of patients on LTOT were poor, especially if a nonpulmonary physician initiated LTOT. We recommend that more attention should be paid on proper monitoring of LTOT, and that only chest physicians should be able to prescribe and re-evaluate LTOT.