In patients with non-valvular atrial fibrillation one must differentiate between those without a clinically suspected embolic event and those who have sustained embolism or stroke of uncertain origin. All of the latter should undergo echocardiography as part of a comprehensive search for a possible source of embolism. A positive finding will enhance the probability that the ischaemic event was indeed caused by a cardiac embolus. It must be kept in mind, especially in stroke patients, that long-term anticoagulation will expose many of them to a far higher risk of haemorrhage [26] due to multimorbidity, propensity to repeated falls and difficulties in compliance than it did to the carefully selected cohorts of the recent warfarin studies. Whenever transthoracic echocardiography (TTE) fails to disclose an unequivocal cardiac source of embolism, transesophageal echocardiography (TEE) should be performed. In persons with atrial fibrillation but no history of systemic embolisation the only rationale for performing echocardiography is to rule out heart disease in clinically suspected lone atrial fibrillation. For the rest of this group TEE remains an investigative tool.