Magnesium has been implicated in the pathogenesis of myocardial infarction and its complication like arrhythmia. Magnesium improves myocardial metabolism, inhibits calcium accumulation and myocardial cell death. It improves vascular tone, peripheral vascular resistance, after load and cardiac output, reduces cardiac arrhythmias and improves lipid metabolism. Magnesium also reduces vulnerability to oxygen derived free radicals,improves endothelial function and inhibits platelet aggregation and adhesion.  Objective To know the relationship between the serum magnesium levels and arrhythmias in patients with acute myocardial infarction.  Method By using simple random method, 60 cases of acute myocardial infarction admitted in KATURI MEDICAL COLLEGE & HOSPITAL,GUNTUR over a period of 11 months,i.e., between July 2021 to may 2022.  Results There is significant difference in Magnesium levels inpatients with and without arrhythmias.  Conclusion In acute myocardial infarction, patients with low magnesium levels are more prone to get arrhythmias. So magnesium treatment can be considered in patients of acute myocardial infarctionwith low magnesium levels.