Evaluation of the first 100 patients with mitral regurgitation corrected by an open technic using the heart-lung machine and studied from 6 months to 3.5 years later demonstrated an operative mortality of 9% for patients with pure regurgitation; 80% of living patients were markedly improved, 20% showed fair improvement. Patients with predominant regurgitation had an operative mortality of 12%; 80% were markedly improved, 20% showed fair improvement. Patients with predominant stenosis had an operative mortality of 10%; and all survivors showed excellent improvement. The majority of patients had some reduction in heart size and an improvement in ecg and murmurs. Over 70% had hemodynamic benefit. Greater benefit may be possible with earlier operations.