Atrial fibrillation (AF) is the most commonly sustained arrhythmia and it is the most heterogeneous arrhythmia with regard to the individual spectrum of resulting symptoms. Assessment of quality of life has received increasing attention as an outcome measure of the subjective sequelae of the disease. At present, conclusive data concerning the prognostic benefits of any therapeutic intervention are lacking, with the exception of the proven need for antithrombotic treatment. Therefore, assessment of any benefit from treatment in the management of patients with AF depends on documentation of symptomatic improvement. Exercise tolerance, duration of sinus rhythm after cardioversion and number of relapses with paroxysmal AF, for example, have been used as study end-points for evaluating different therapeutic modalities. Although these factors - as assessed in controlled studies reflect some effect of treatment, these surrogate end-points were often not accompanied by appropriate measurements of the subjective improvement in patients' symptoms. Health-related quality of life is a summarized outcome assessment that is designed to reflect the subjective impairment in general well being caused by individual aspects of pain, and psychological, emotional and physical disturbances. In addition, measures of quality of life take into consideration the potential burdens and side effects of any treatment that leads to improvement in specific symptoms but that may negatively affect general well being. This paper reviews currently available data on the assessment of quality of life in patients with AF Furthermore, the definition and usefulness of different clinical patterns and classifications of AF with regard to quality of life are discussed. Finally, toots and definitions for further clinical research are suggested. (C) 2003 The European Society of Cardiology. Published by Elsevier Science Ltd. All rights reserved.