Nine patients with clinical and hemodynamic evidence of cardiac tamponade underwent M-mode and two-dimensional echocardiography. Pericardial effusion was documented in each patient. Four patients demonstrated respiratory variation in ventricular volumes in association with paradoxical pulse. Right ventricular compression was present in seven. In five patients, echocardiography demonstrated diastolic left atrial compression. In all nine patients, the apical four chamber view revealed diastolic right atrial compression. Drainage of 450 to 1,800 cc of pericardial fluid relieved the cardiac tamponade and eliminated the echocardiographic findings associated with this disorder. These observations suggest that the echocardiographic findings of atrial compression is a sensitive sign of cardiac tamponade.