Stroke is a serious complication of atrial fibrillation, affecting not only the patient but people around them as well. It has a huge financial impact on the NHS. The use of warfarin reduces ischemic stroke but should not be taken lightly as the drug is associated with increased risk of haemorrhage. Drs Anil K Agarwal, Ranjna Garg, S A Kauser and Stuart Hutchinson look at the current status of warfarin use in the prevention of stroke in atrial fibrillation.