BACKGROUND/AIMS: Although the impact of ST segment elevation in patients with acute myocardial infarction (MI) has been studied, little information is available on the impact of ST segment elevation in the patients with acute MI and left ventricular systolic dysfunction. METHODS: We retrospectively analyzed the baseline clinical and angiographic characteristics and the in-hospital and 1- year clinical outcomes of 117 consecutive patients who were diagnosed with acute MI and who had a left ventricular ejection fraction of less than 40%, and these patients were treated from January 2004 to June 2006 at Busan Paik Hospital. Coronary angiography at the index hospitalization and the major adverse cardiac events (MACEs), including cardiac death, non-fatal reinfarction, target vessel revascularization (TVR), and heart failure, were compared between the 77 patients with ST segment elevation myocardial infarction (STEMI) and the 40 patients with non-ST segment elevation myocardial infarction (NSTEMI). RESULTS: Overall, the baseline clinical characteristics were similar between the two groups. On the coronary angiography, thrombolysis in myocardial infarction 0 flow was more common in the STEMI group as compared to the NSTEMI group (p<0.01) and the NSTEMI group had more frequent multivessel disease compared to the STEMI group (p=0.01). However, the in-hospital cardiac deaths and MACEs were not different on comparison between the two groups (p=0.66, p=0.81, respectively). The one-year cardiac deaths and MACEs were not significantly different on comparison between the two groups (p=0.37, p=0.68, respectively). CONCLUSIONS: This study demonstrated that ST segment elevation had no influence on in-hospital and the long term outcomes of patients with acute MI and left ventricular systolic dysfunction.