Real time two dimensional echocardiography was performed in five patients with constrictive pericarditis. The echocardiogram showed several typical features: (1) The heart was normal in size or decreased; the ventricles were small and the atria enlarged. (2) The pericardium was seen as a single or double dense rigid shell surrounding both ventricles and the apex; its immobility was striking. (3) The inferior vena cava and hepatic veins were greatly dilated in keeping with the severe clinical venous congestion. (4) Both interventricular and interatrial septa bulged into the left side of the heart on inspiration. (5) The atrioventricular valves were hypermobile. (6) A prominent ventricular diastolic filling half was seen. The two dimensional echocardiogram excluded other causes of severe cardiac failure such as congestive cardiomyopathy and valvular heart disease, while the dense immobile pericardial echo or echoes and the "normal" texture of the myocardial echoes made the diagnosis of restrictive cardiomyopathy unlikely.