In mitral valve disease, left atrial thrombus is a common finding, particularly in left atrial appendage in patients with atrial fibrillation. But free-floating thrombus is rare. Nevertheless, it is an important and potentially fatal complication because it can cause sudden arrest by obstucting the mitral orifice, or serious cerebral and peripheral embolic events. Therefore it is important to early detect such lesions. It usually occurs in the setting of a large, dilated left atrium with stagnant flow, commonly the result of severe rheumatic mitral stenosis and accompanying atrial fibrillation. We report the clinical and echocardiographic findings in a patient with left atrial free-floating thrombus who had two episodes of cerebral embolic event.