OBJECTIVE: The purpose of this study was to define the effect of the changes of left ventricular ejection fraction (LVEF) on long-term major adverse cardiac events (MACEs) in patients with acute myocardial infarction (AMI). METHODS: Clinical analysis was performed on 1,188 AMI patients who completed follow- up 2-dimensional (2D) echocardiography after one year and clinical follow-up for 5 years. These patients were divided into three groups according to the LVEF change ratio: group A [increased LVEF change ratio, N=626], group B [decreased LVEF change ratio<20%, N=414], group C [decreased LVEF change ratio≥20%, N=148]. RESULTS: Initial low LVEF group and normal LVEF group showed no differences in MACEs. The mean initial and follow-up LVEF were 54.4±12.2% and 60.4±12.3% in the group A, 54.6±13.0% and 47.9±12.1% in the group B, and 56.5±12.6% and 39.9±11.6% in the group C (p=0.71). Total MACEs occurred in 62 (9.9%) patients in the group A, 83 (20.0%) patients in the group B, 44 (29.7%) patients in the group C during 5-year clinical follow-up (p=0.01). Initial low EF (<45%) was not a risk factor for long-term MACEs (Odd ratio (OR), 1.686; 95% confidence index (CI), 0.861-2.862, p=0.065), but the LVEF change ratio was a strong risk factor for long-term MACEs (OR, 3.731; 95% CI, 2.039-6.828, p=0.001). MACE-free survivals of patients with initial low LVEF and patients with low LVEF during follow-up period showed no significant differences (p=0.731). CONCLUSION: Initial low LVEF is not a predictor of long-term MACEs, but the decreased LVEF ratio during follow-up period is a strong predictor of long-term MACEs.