Mitral regurgitation (MR) is common in patients with congestive heart failure (CHF), but the frequency in relation to the origin of ventricular dilatation has not been established. In 50 patients referred for cardiac transplantation, MR was assessed by Doppler echocardiography and the findings were compared with clinical information. Dilatation of the left ventricle, left atrium and mitral anulus was analyzed in 25 patients with respect to cause of CHF. All 50 patients had MR of at least moderate severity, regardless of cause (idiopathic dilated cardiomyopathy in 36, coronary artery disease in 14), length of symptoms (20 +/- 19 months, less than 6 months in 13 patients) or presence of murmurs (absent in 13 patients). Comparison of patients with nonischemic cardiomyopathy to those with ischemic heart disease revealed larger left ventricular volumes (215 +/- 81 vs 131 +/- 60 ml in systole, p less than 0.05) and left atrial volumes (124 +/- 70 vs 70 +/- 35 ml, p less than 0.05). Mitral anular dilatation was present only in patients with idiopathic cardiomyopathy (diameters 3.6 +/- 0.4 vs 3.1 +/- 0.2 cm, p less than 0.05). The frequency of significant MR in these patients with CHF suggests that it may have a major role in decompensation and in the therapeutic response.