Free-floating left atrial ball thrombus is an extremely rare and serious disorder that 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. In the present case, we report a free-floating left atrial ball thrombus developed in an 11-year-old child with idiopathic restrictive cardiomyopathy during sinus rhythm and manifested as peripheral arterial embolic event. To our knowledge, this is the first case of free-floating left atrial ball thrombus developed in a patient with restrictive cardiomyopathy. Furthermore, this also is the first case of free-floating left atrial ball thrombus developed in a patient during sinus rhythm. (c) 2005 Elsevier Ireland Ltd. All rights reserved.