BACKGROUND: The management of atrial fibrillation (AF) has changed substantially in recent years, especially with a greater appreciation of the prophylactic role of antithrombotic therapy against stroke. There is therefore a need for further information on the prevalence of AF in Britain, the prevalence of (and contraindications to) anticoagulant treatment, and the factors that influence doctors' decisions in treating AF, including the investigation of patients with this arrhythmia. AIM: To investigate the prevalence, clinical features and management of patients with AF in a general practice setting. METHOD: Cross-sectional survey of patients using treatment prescriptions and clinical records in two general practices from the west of Birmingham (serving a patient population of 16,519) where 4522 subjects (27.4%) were aged > or = 50 years. RESULTS: One hundred and eleven (2.4%) patients who were aged > or = 50 years were found to be in AF (42 males; mean age 76.6, SD 9.1); 77.5% were Caucasian, 2.7% Afro-Caribbean, 0.9% Asian, and 0.9% mixed race; in 20 cases there was no information on ethnicity. Of the AF patients, 5.4% were aged 50-60 years, 16.2% aged 61-70 years, 20.7% aged 71-75 years, 20.7% aged 76-80 years, 24.3% aged 81-85 years, and 12.6% aged > 85 years old, with female patients being significantly older than males. Eighty-one patients (73%) had chronic AF, while 30 patients (27%) had paroxysmal AF. The most common associated factors were hypertension (36.9%) and ischaemic heart disease (28.8%), with no obvious cause for AF in six patients. Cardiac failure was associated with AF in 34 patients (30.6%), and stroke had occurred in 29 patients (18%). Only 20 patients (18%) had had an echocardiogram, 26 (23.4%) a chest X-ray, and 58 (52.3%) thyroid function test. Only 30.6% had ever presented to hospital practice. Warfarin was prescribed to 40 patients (36%), with anticoagulation intensity monitoring by the general practitioner (GP) in three cases (7.5%), by a hospital clinic in 30 (75%), and by both GP and hospital in seven cases (17.5%). Of those not anticoagulated (n = 71), only 12 patients (16.9%) had contraindications to warfarin therapy. Patients treated with warfarin were younger than those who were not prescribed warfarin (71.3 versus 79.6 years, P < 0.001). Aspirin was being prescribed for 21 patients (18.9%), primarily for previous myocardial infarction. Only five patients (4.5%) had ever had attempted cardioversion. CONCLUSION: Atrial fibrillation is a common arrhythmia in general practice, and is commonly associated with hypertension, ischaemic heart disease and heart failure. There is a suboptimal application of standard investigations and use of antithrombotic therapy or attempted cardioversion; and few patients have presented to hospital practice. Guidelines on the management of this common arrhythmia in general practice are required.