Anticoagulation is a treatment with significant and life threatening complications requiring that the balance of risk and benefit be individually assessed in each patient. The risks are greater in the elderly and those with hypertension, falls and gastrointestinal disease. The use of anticoagulants is now established in patients with symptomatic non-rheumatic atrial fibrillation, especially older patients with hypertension, cardiac failure or a large left atrium or left ventricular dysfunction. There is, however, no place for the routine use of anticoagulants in acute stroke or as part of secondary prevention in patients in sinus rhythm. There may be a place, though as yet the evidence would not support this, for the limited use of anticoagulants in special situations such as cortical venous thrombosis or carotid dissection.