Recent studies have shown that rheumatic heart disease is no longer the main cause of isolated severe pure mitral regurgitation. In this study, we evaluated various clinical and echocardiographic features found in the syndrome of mitral regurgitation. Our data is consistent with recent reports that mitral valve prolapse and coronary artery disease are now the predominant causes of mitral regurgitation and that rheumatic heart disease is a much less common etiology. In addition, our data suggest that clinical evaluation alone is usually very accurate in identifying the correct etiology. Various clinical and echocardiographic features found in the subsets of acute and chronic mitral regurgitation are described. Specifically, patients with acute mitral regurgitation were more likely to have echocardiographic evidence of segmental left ventricular dysfunction and flail mitral valve leaflet. In chronic mitral regurgitation, atrial fibrillation and left atrial dilatation were more commonly present. Echocardiography was found to be more useful in the detection of the complications of coronary artery disease rather than in identifying its presence. Patients with a New York Heart Association classification of IV and those with echocardiographic evidence of an increased left ventricular endsystolic dimension or left ventricular hypertrophy had a worse prognosis.