Ten patients with isolated right atrial tamponade complicating open heart surgery were identified over a 3.5-year period at three institutions. Clinical manifestations varied but were typically those of decreased perfusion with elevated central venous pressure. Hemodynamically these patients had systemic hypotension and tachycardia with elevated central venous pressure but without elevation of pulmonary artery or pulmonary artery wedge pressures. The correct diagnosis in each case was established by echocardiography; 7 via the transthoracic and 3 via the transesophageal approach. The typical echocardiographic feature was an extrinsic extracardiac mass compressing the atrium. Doppler findings included high flow velocities through the right atria, and color flow demonstrated narrow color jets through compressed, slit-like right atria. Surgical exploration confirmed these findings in each case. We conclude that the combination of clinical awareness and appropriate hemodynamic evaluation can alert the physician to the possibility of isolated right atrial hematoma causing decreased perfusion and/or shock following open heart surgery. Echocardiography using either the transthoracic or transesophageal approach can establish the diagnosis and lead to timely surgical intervention.