Forty-six patients who underwent mitral valve replacement for mitral regurgitation due to coronary artery disease during 1970-1975 were identified. Forty patients underwent aortocoronary bypass procedures at the same operation. The survival rate at the fourth postoperative year was 73% in the 22 patients in whom the preoperative left ventricular ejection fraction exceeded 0.35, 38% in the 16 patients in whom the preoperative left ventricular ejection fraction was 35% or less, and 25% in the eight patients in whom aneurysmectomy was performed at the time of mitral valve replacement (p < 0.05 for the former group compared to the latter two groups). Heart failure, present preoperatively in 41 patients, was improved in most of the longterm survivors. Neither the angiographic extent of coronary artery disease nor whether mitral valve replacement was performed in the acute (within 2 months in 13 patients) or chronic phase of myocardial infarction were distinctly correlated with survival.