An emergency observation department unit (EDOU) treatment protocol for the management of acute atrial fibrillation (AAF) has been demonstrated to be feasible in the United States of America. The aim of this study was to quantify the number of patients presenting with AAF eligible for EDOU protocolized management in an Irish hospital. A retrospective observational study was performed by identifying a sample of patients admitted to hospital with acute atrial fibrillation between January and December 2002. Medical records of one hundred and eleven patients presenting with AAF were identified. Nine patients were eligible for EDOU management. Fourteen patients (12.6%) reverted spontaneously to sinus rhythm in the ED without medical intervention. Eight percent of patients presenting with AAF in an Irish hospital are eligible for protocolized EDOU management.