Background and Objectives : Clinical significance of J wave in patients with myocardial infarction (MI) has not been well elucidated. We hypothesized that existence of J wave in inferior leads and/or its reciprocal wave in leads V1-3 is associated with poor prognosis of the patients with inferior wall MI. Subjects and Methods : Total 321 consecutive patients with inferior wall acute MI (AMI) who underwent coronary intervention in a single center were enrolled. ECG obtained 1 day after AMI was assessed by two independent cardiologists in each patient. The ECGs were categorized into 4 groups according to the J wave location: inferior leads only (group A, n=55, 17.1%), negative J wave in V1-V3 only (group B, n=15, 4.7%), in both inferior and V1-3 leads (group C, n=30, 9.3%), and none (group D, n=221, 68.8% ). The primary end point was all-cause mortality and the secondary end point was cardiac death. Results : Total 30 patients died and among them 19 were from cardiac causes. Although all-cause mortality was significantly different between groups with J waves in inferior and/or V1-3 leads and those without J waves, [A+B+C(J wave,n=14(14%))vs.D(n=16(7%)):p=0.05, A+C(inferior J wave, 12(14%))vs.D(n=16(7%)):p=0.06, B+C(negative J wave, 7(16%))vs.D(n=16(7%)): p=0.08] , cardiac mortality had no significant difference [A+B+C(J wave,11(11%)) vs. D(8(4%)):p=0.11, A+C(inferior J wave, 9(11%)) vs.D(8(4%)):p=0.18, B+C(negative J wave, 6(13%)) vs.D(8(4%)):p=0.13]. When compared between each groups, there was a significant difference in all-cause mortality between group C and D (p-value; Avs.B:0.62, Avs.C:0.42, Avs.D:0.15, Bvs.C:0.57, Bvs.D:0.32, Cvs.D:0.09), but no significant difference in cardiac mortality among the groups.(significance level=0.1) Conclusion : Presence of J wave in inferior leads and/or its reciprocal wave in leads V1-3 is associated with higher all-cause mortality in patients with inferior wall MI. [Key word : J wave, cardiac death, myocardial infarction]