Five cases of miscellaneous right atrial mass were described to illustrate the very valuable diagnostic contribution of two-dimensional echocardiography (2DE). Two patients had a large myxoma in the right atrium, and other two had an extension of hepatoma into the right atrium through the inferior vena cava. The fifth patient with a past history of myocardial infarction had a floating right atrial thrombus. The myxoma in the right atrium appeared as a mottled, ovoid, and sharply demarcated mobile mass attached to the interatrial septum. The diagnosis of these two patients was confirmed at operation. The right atrial myxoma in the first case weighed 310 g and filled almost the entire right atrium and right ventricle. To our knowledge, this was the largest myxoma among previously reported cases. The hepatoma extended into the right atrium resembled myxoma, but was obscurely demarcated. The 2DE was useful to localize a large immobile mass extending into the right atrium. All these right atrial tumors were adequately demonstrated in the right lateral decubitus position with the transducer over the right parasternal position. In the fifth case, bedside real-time 2DE was performed after the attack of pulmonary thromboembolism, and an irregular echogenic mass was seen to float freely, suggesting a thrombus. Following the immediate anticoagulant therapy with heparin, the thrombus echo was no longer visible by 2DE. It was concluded that 2DE should be extensively applied to diagnose right atrial tumors or thrombi.