A prospective interventional study was carried out to compare the thrombolytic effect of streptokinase between diabetic and non-diabetic myocardial infarction patients. Out of 187 study subjects with acute ST segment elevation myocardial infarction, admitted at coronary care unit, 126 patients were nondiabetic and 61 patients were diabetic. Streptokinase was administered to all patients. Resolution (reduction) of elevated ST segment was evaluated after 90 min of streptokinase administration. Successful reperfusion (≥70% ST-resolution) was significantly higher in non-diabetic than diabetic (p<0.001), while failed reperfusion (<30% ST resolution) was significantly higher in diabetic patients (p<0.001). It may be concluded that diabetes mellitus might affect the thrombolytic outcome of acute myocardial infarction patients with diabetes mellitus.