reasons for underuse of oral anticoagulation in atrial fibrillationassociated stroke prospective study of german stroke patients oral anticoagulation in atrial fibrillation af is effective in primary and secondary prevention of cardioembolic stroke but is often underused in practice the detailed reasons for nonuse of oral anticoagulation are less well known we prospectively analyzed 105 consecutive cases of acute ischemic stroke associated with atrial fibrillation patients were investigated by a semistructured interview the most frequent reasons for underuse were unknown af 43 in case of known af reluctance of patients 30 contraindications 25 and compliance problems 20 there was good agreement between patients and physicians views about nonuse or aborted use of oral anticoagulation kappa 064 and 093 respectively unknown atrial fibrillation is the most prevalent cause of underutilization of oral anticoagulation in acute stroke patients since atrial fibrillation is easy to detect in most cases it could be worthwhile to screen elderly patients without contraindications for anticoagulation