- BACKGROUND AND PURPOSE: Despite the publication of a number of randomized, controlled trials demonstrating a substantial reduction in stroke with anticoagulation in patients with nonvalvular atrial fibrillation, the 'real world' use of warfarin is sub-optimal. Previous surveys have attempted to explain this problem but have significant limitations. The purpose of this study was to assess the relative importance of various barriers that may influence the prescription of warfarin in patients with nonvalvular atrial fibrillation. METHODS: This cross-sectional survey was mailed to all practising cardiologists, neurologists and internists, as well as a random sample of family physicians within Alberta. Physicians caring for patients with NVAF rated the relative importance of potential barriers using a Likert scale. RESULTS: Sixty-seven per cent of all physicians returned the survey. Overall, barriers pertaining to the patient's clinical characteristics were rated to be more important than those pertaining to the physician or to the organization required when prescribing these therapies. Specifically, an ongoing history of falls, a history of bleeding within the previous year and an inability to comply with therapy were rated as important barriers by 64%, 55% and 53% of physicians, respectively. Most physicians strongly believed that patients should receive information on the benefits and risks of warfarin (96%) and that patients should have a say in whether warfarin is prescribed (86%). IMPLICATIONS: This study suggests that most of the barriers to warfarin use pertain to patient clinical characteristics and the need for patients to be involved in the decision to initiate therapy. The use of decision support technologies would facilitate involvement of the patient and serve to educate both the patient and physician on the risks and benefits of warfarin therapy.