The echocardiographic features and management of 10 children with right heart thrombus (RHT) are presented. The patients' ages ranged from 2 weeks to 12 years. Three patients were less than 3 weeks old. The echocardiographic diagnosis was confirmed in five patients by surgery or autopsy. The thrombus was detected in the right atrium (five patients), in the right ventricle (three), on the tricuspid valve or within the inferior vena cava, the superior vena cava, or its extension following Senning's operation for transposition of great arteries (TGA). Seven patients had structural heart disease: TGA in four, tricuspid atresia in three. In two of three patients with anatomically normal heart, the thrombus occurred as a complication of a ventriculoatrial and a lymphovenous shunt system. The third patient had no predisposing factor. Five patients were treated with anticoagulants or platelet anti-aggregating agents and four by surgery. Seven patients survived and were followed by echocardiography.