Aims: To develop a practical patient-completed chronic obstructive pulmonary disease assessment questionnaire (COPD-AQ) to improve COPD assessment and management in primary care, based on the concept of COPD stability. Methods: An Expert Working Group defined parameters of COPD stability and a 10-item Physician's Global Assessment was established. A 21-item COPD-AQ was developed and validated in a cross-sectional, non-randomised study of patients with COPD (n=395). Items most discriminative of stability status (stable/unstable) were selected to produce a 5-item COPD-AQ, which was then validated. Results: In the development sample, internal consistency reliability of the 5-item COPD-AQ was 0.74 (n=296). The COPD-AQ discriminated between stability groups based on physician assessment (F=44.26; p<0.0001) and post-bronchodilator spirometry measures (F=2.92; p<0.05). A questionnaire score >20 (range: 5.0-25.0) had a specificity of 82.9% and sensitivity of 64.7%. Conclusions: The 5-item COPD-AQ proved a practical tool for assessing COPD status and was sufficiently simple for routine clinical use. However, overall validation was limited by small numbers of patients in the validation sample. Difficulties also existed over using the term 'stability' to define COPD status. COPD-AQ was not progressed further, but this work will prove valuable in the future development of a global questionnaire to improve COPD management in primary care. © 2009 General Practice Airways Group. All rights reserved.