Clinical audit has an important role as an indicator of the clinical practice in a given community. The European Respiratory Society (ERS) chronic obstructive pulmonary disease (COPD) audit was designed as a pilot study to evaluate clinical practice variability as well as clinical and organisational factors related to outcomes for COPD hospital admissions across Europe. The study was designed as a prospective observational noninterventional cohort trial, in which 422 hospitals from 13 European countries participated. There were two databases: one for hospital's resources and organisation and one for clinical information. The study was comprised of an initial 8-week phase during which all consecutive cases admitted to hospital due to an exacerbation of COPD were identified and information on clinical practice was gathered. During the 90-day second phase, mortality and readmissions were recorded. Patient data were anonymised and encrypted through a multi-lingual web-tool. As there is no pan-European Ethics Committee for audits, all partners accepted the general ethical rules of the ERS and ensured compliance with their own national ethical requirements. This paper describes the methodological issues encountered in organising and delivering a multi-national European audit, highlighting goals, barriers and achievements, and provides valuable information for those interested in developing clinical audits.