Aim: to determine the efficacy of thrombolytic therapy with IV streptokinase in acute ST elevation myocardial infarction patients. Methods: A prospective observational study was conducted in the Department of Cardiology, Indira Gandhi Institute of Medical Science, Patna, Bihar, India for 12 months. Total 90 Patients with diagnosis of acute ST segment elevation before and after thrombolysis with Streptokinase Were included in this study. Based on values obtained, study population divided into three categories. Category A: <30% resolution of the sum of ST segment elevation. Category B: 30%-70% resolution of the sum of ST segment elevation. Category C: >70% resolution of the sum of STsegment elevation. Results: In the present study, the minimum age of the patient is 30 years, maximum age is 76 years. Maximum numbers of patients in between 40-60 years constitute 55%. Mean age of present study is 51.81±9.5. Male patients were significantly increased (77.78%) when compared with Female patients (22.22%). The chest pain was the most common mode of presentation, present in 84 (93.33%) patients associated with sweating in 79(87.78%) patients, breathlessness seen in 22 (24.44%) patients. Syncope was seen in 10 (11.11%) patients and palpitation in 5 (5.55%) patients. In this study anterior wall Myocardial infarction was not significant compared with inferior wall myocardial infarction. Complete ST resolution seen among 40% cases, partial resolution seen among 45.55% and no resolution among 14.44% cases. Thrombolysis time of <3 hours, 3-5 hours and more than 5 hours was noted in a, b and c categories patients. B and c categories patients were significantly increased when compared with a categories patients. Conclusion: In the present study we conclude that the efficacy of IV streptokinase for thrombolysis in acute STEMI is 40%. Patients with no resolution of ST segment 90 minutes following thrombolysis associated with more frequent adverse events and increased mortality compare to partial and complete resolution group.