The effect of opium addiction on the appearance of different types of arrhythmias after acute myocardial infarction (AMI) has been assessed in few studies. This study is aimed to determine the effect of opium on post-MI arrhythmia and also to address the differences in the appearance of different types of arrhythmias after AMI between opium addicted and non-addicted patients. In this comparative study, participants were classified into two groups with opium addiction (n=94) and without opium addiction (n=106). Post-MI arrhythmias were determined among each group. Study populations were included all patients with first AMI admitted within 6 hours of the onset of chest pain to coronary care units (CCU) of two teaching hospitals affiliated to Kerman University of Medical Sciences (KUMS) in the city of Kerman, Iran. Opium addicted subjects had significantly more frequency of arrhythmia than non-opium addicted subjects (80.9% vs. 22.6%, respectively; P