Myocardial performance index (MPI) is a numeric value, which could be obtained by using cardiac time intervals. This numeric value is defined as the sum of isovolumetric contraction time (ICT) and isovolumetric relaxation time (IRT) divided by ejection time (ET) and could be calculated for each ventricle individually. Myocardial performance index has been invented as a Doppler index of combined systolic and diastolic myocardial performance in patients with primary myocardial systolic dysfunction. Myocardial performance index has prognostic value in various clinical settings seems to be independent of heart rate. In this review, clinical applications of MPI are scrutinized.