Data from cardiac catheterization at rest and during exercise in 57 patients with dilated cardiomyopathy (DCM) were analyzed to evaluate the bearing of mitral regurgiation (MR) detected by color Doppler echocardiography (CDE) on prognostically important invasive hemodynamic parameters and survival. The etiology of DCM was coronary artery disease in 21 patients and unproven (‘idiopathic’) in 36 patients. MR was detected by CDE in 34 patients (60%) with an agreement of 93% compared to left ventriculography. Mean age, etiology of DCM and duration of symptoms were similar in patients with and without MR, while patients with MR were in a higher NYHA class, had lower ejection fraction (LVEF) (25 ± 13 vs. 35 ± 17%; p < 0.02), larger left ventricular volumes (356 ± 138 vs. 268 ± 61 ml; p < 0.01) and higher left ventricular end-diastolic pressure (LVEDP) (21 ± 9 vs. 13 ± 7 mm Hg; p < 0.01). At rest, right-sided pressures were higher in patients with MR compared to patients without MR (pulmonary wedge pressure 20 ± 9 vs. 10 ± 3 mm Hg, mean pulmonary arterial pressure 30 ± 11 vs. 20 ± 8 mm Hg, mean right atrial pressure 9 ± 4 vs. 4 ± 2 mm Hg, all p < 0.001), but no significant differences were found in cardiac index (CI) or stroke index (SI). During supine bicycle exercise (increasing heart rate by 50%), both groups demonstrated a similar rise in right-sided pressures, while the patients with MR exhibited a lower increase in CI (3.5 ± 1.8 vs. 4.4 ± 1.41iters/min/m<sup>2</sup>;p < 0.05) and were unable to increase SI. When survival after 1 year was analyzed as a ‘worst-case situation’ (cardiac transplantation equals death), survival was significantly lower in patients with MR (14/34 vs. 1/23; p < 0.01). CDE is a noninvasive and accurate method for detection of MR; it is valuable for early risk stratification, being a marker of the subset of patients with DCM having reduced ventricular function and a poor prognosis.