Atrial fibrillation (AF) is an important and independent risk factor for stroke, particularly in elderly people. The efficacy of treatment with warfarin and aspirin in primary and secondary stroke prevention in AF has been demonstrated in randomized clinical trials. In a demographic study, we examined the prevalence of AF in patients registered with a general practice in the North East of England; 91 patients with known AF were identified, 69 with chronic AF and 22 with paroxysmal AF. The mean duration of the arrhythmia was 6.43 years and the prevalence of AF increased with age. There was a high prevalence of cerebrovascular disease in AF patients. The majority of AF patients were not receiving therapy with aspirin or warfarin as primary or secondary stroke prevention. If strategies for stroke prevention in AF are to be applied to the community, general practitioners will need to play a more active part.