Atrial fibrillation (AF) is a very common problem. In England alone, approximately 835,000 people have AF.321 Through its effects on rate and rhythm, it is a major cause of morbidity. Through increasing susceptibility to stroke, it is a major cause of both morbidity and mortality. Despite the fact that AF is a major population problem, it is not necessarily well managed. Anecdotally, people with AF often describe the inadequate explanations they have been given at the time of first diagnosis both concerning the nature of the problem and the treatment options which are open to them. This may partly reflect the fact that many doctors, particularly those working in primary care, do not feel confident in AF management. Anticoagulation is a case in point. The 2006 atrial fibrillation NICE Guideline laid down criteria for anticoagulation – yet amongst patients with known AF, only 55% of those fulfilling the 2006 criteria for anticoagulant therapy currently receive it. Research into the shortfall in anticoagulant uptake indicates that it cannot be adequately explained by either bleeding risk or co-morbidities. The attitude of healthcare professionals and the perceived risk of anticoagulation could also be major factors limiting uptake. The shortfall in the prescribing of anticoagulants to patients with AF was clearly seen in the Sentinel Stroke National Audit Programme of the Royal College of Physicians. Of 11,939 patients admitted with stroke to hospitals in England, Wales and Northern Ireland in the first 3 months of 2013, approximately one fifth were in AF on admission. Of these only 36% were receiving an anticoagulant. Yet 38% were on an antiplatelet drug as sole antithrombotic therapy and 26 % were on no antithrombotic treatment. The rate and rhythm management of AF is also often perceived to be difficult. In discussions informing the scope of this guideline, the classification of AF into paroxysmal, persistent and permanent was considered to be a barrier to implementation of rate and rhythm care. While this classification is a natural sub-division which does help to inform management, it is important that it should not obscure the common underlying principles of heart rate and rhythm care which apply to the generality of AF patients. This guideline seeks to address these issues. The question of how best to provide a patient with a focussed care package including patient information and treatment options is considered. Stroke prevention is considered in detail both in terms of treatment strategies, risk thresholds and risk scoring and options for treatment. Finally rate and rhythm management are considered, in as far as possible based on the totality of AF, rather than on individual sub-categories. In considering rate and rhythm management, it is emphasised that patient symptoms should be the driver to timely consideration of alternative escalating management options. No clinical guideline can ever be complete and the constraints of the guideline process have meant that we have needed to focus on a number of specific areas. The current guideline is a partial update of the 2006 guideline. The evidence relating to some sections of the 2006 guideline, most particularly AF diagnosis, has not been updated and the original recommendations have been incorporated unchanged. It is also the case that there has been very rapid progress in a number of areas relating to AF in recent years. This has been reflected in recent NICE technology appraisals on dronedarone, dabigatran, rivaroxaban and apixaban. The evidence and the recommendations relating to these drugs have not been reconsidered in the current guideline. The existing technology appraisal recommendations have been incorporated into the updated guideline. We have not sought to distinguish which aspects of care should take place in specific settings. We recognise that models of care vary greatly both locally and nationally and that in many places aspects of AF care which might hitherto have been regarded as most suited to secondary care are now being undertaken in primary care. It seems likely that this trend will continue. We have therefore tried to avoid imposing artificial boundaries. The target audience of the guideline is any healthcare professional working in any setting who is involved in caring for patients with AF.