The long-term clinical outcome was assessed in 22 patients (15 men and 7 women; mean age, 68 years) who underwent mitral valve replacement or repair for acute mitral regurgitation due to postinfarction rupture of a papillary muscle during the period 1981 through 1990 at the Mayo Clinic. All but three patients underwent operation within the first 3 weeks after acute myocardial infarction. The perioperative mortality was 27%, and the estimated actuarial survival rate at 7 years postoperatively was 47% and 64% for the entire group and for the patients who survived the operation, respectively. The concomitant performance of a coronary artery bypass grafting procedure was the only factor identified that improved both immediate and long-term survival. Patients with a decreased preoperative left ventricular ejection fraction (less than 45%) had somewhat greater short-term and long-term mortality than did those with a left ventricular ejection fraction of 45% or more, but the difference was only of borderline statistical significance. Other factors such as age, sex, severity of coronary artery disease, preoperative existence of congestive heart failure, and timing of the operation in relationship to occurrence of the infarction had no effect on survival. Of the 13 long-term survivors, 10 had significant clinical improvement in comparison with their preoperative state.