The authors analyzed data from 15 patients with idiopathic dilated cardiomyopathy to evaluate the hemodynamic changes and left ventricular cineangiogram as compared with normal control. Mean right atrial pressure, right ventricular systolic pressure, mean pulmonary artery pressure and mean pulmonary wedge pressure were signigicantly elevated in patients with dilated cardiomyopathy. Left ventricular enddiastolic volume was increased in idiopathic dilated cardiomyopathy(139.9+/-58.73 ml/m2). Cardiac index, left ventricular ejection fraction and circumferential fiber shortening were significantly reduced in patients with dilated cardiomyopathy as compared with normal control(p<0.001). Hypokinetic, diffuse wall motion abnormalities of left ventricle were common in idiopathic dilated cardiomyopathy. A few cases of akinetic or dyskinetic segmental wall motion abnormalities were present. Left ventricular configurations in patients with idiopathic dilated cardiomyopathy were globe shape(53.4%) as compared with pear core shape(90%) of normal control. Associated mitral regurgitations in patients with idiopathic dilated cardiomyopathy confirmed by left ventricular cineangiogram were 53.3 percent. Mild to moderate mitral regurgitations were often present(46.6%).