BACKGROUND: Long-term survival after surgical correction of mitral regurgitation is associated with preservation of left ventricular systolic function after operation. And mitral valve repair has been suggested to provide a better postoperative left ventricular systolic function. Accordingly, we intended to compare the operative results of mitral valve repair with those of mitral valve replacement and search for preoperative predictors of postoperative left ventricular systolic function. METHOD: The clinical features, echocardiographic measurements, and cardiac catheterization results of 75 patients operated between January 1984 and December 1994 for acquired pure mitral regurgitation were analyzed. RESULTS: Of the 75 patients, 39 patients had mitral valve repair, and 36 patients had mitral valve replacement. When the outcomes of mitral valve repair and mitral valve replacement were compared, left ventricular ejection fraction decreased significantly after surgery inboth groups but postoperative left ventricular ejection fraction was greater in valve repair group than in valve replacement group. Data analysis of preoperative variables showed that echocardiographic left ventricular end-diastolic diameter(p<.05), but not other clinical and echocardiographic variables, were predictors of postoperative left ventricular systolic function. CONCLUSION: After surgical correction of chronic organic mitral regurgitation, left ventricular dysfunction is frequent and valve repair decreases the severity of left ventricular dysfunction. And the most powerful predictor of postoperative left ventricular systolic function is preoperative left ventricular end-diastolic diameter measured by echocardiography.