Myocardial infarction (MI)  is one of the dangerous manifestation of coronary artery disease and is one of the most common diagnosis in hospitalized patients of western countries. The determination of location, extent of infarcted myocardium is of vital importance for the prognosis as well as management of the patients. Therefore this present study is conducted to correlate the minimum level of serum magnesium with the enzymatic estimate of infarct size ie. by measuring peak Serum Glutamate Oxaloacetate Transaminase (SGOT) and also with Electrocardiographic estimate of infarct size. Minimum serum magnesium was measured on day 1 of admission to the ICU of 53 patients of acute myocardial infarction. Also 12 lead ECG was recorded from these patients and serum SGOT was measured on for first three days after admission. Statistical analysis for correlation between peak SGOT activity and minimum serum Magnesium was done using Pearson correlation coefficient test . We found statistically significant decrease in serum magnesium and  increase in SGOT activity in patients with widespread myocardial infarction.