Atrial fibrillation (AF) is the commonest sustained cardiac arrhythmia. It is responsible for 30% of hospital admissions for arrhythmia and is a common cause of stroke. Its prevalence increases with age (0.5%: 50–59 years; 8.8%: 80–89 years), with an incidence of 0.2% per year in men aged 30–39 years and 2.3% per year in men aged 80–89 years. It may be associated with cardiac pathology such as rheumatic heart disease, coronary heart disease (CHD), hypertension and cardiomyopathies. When found without such associated conditions, it is called ‘lone’ AF. It frequently complicates non-cardiac conditions such as hyperthyroidism, fever, the post-surgical period, hypoxia and acute ethanol intoxication. In these situations, treatment of the underlying condition may be enough to restore sinus rhythm. However, chronic alcohol abuse can result in a dilated cardiomyopathy of which AF may be the presenting manifestation. The management of AF is changing rapidly, with developments in ablation techniques and implantable devices showing considerable promise. The concept that AF leads to ultrastructural remodelling of the atria, which then further encourages the recurrence and establishment of AF, promotes the application of these and other therapies earlier and more aggressively in the course of the disease than has hitherto been the case.