This study evaluated the effect of intravenous streptokinase therapy on myocardial infarct size retrospectively. For estimating myocardial infarct size we used an electrocardiographic QRS scoring system. The study included 60 patients with acute myocardial infarction admitted within the initial 6 hours. Thirty patients received intravenous streptokinase while the other 30 clinically matched patients constituted the control group. The QRS score of each patient was computed from an electrocardiogram obtained on the day of discharge. The mean QRS score of streptokinase treated group was significantly lower than control group (5.73±0.50 vs 7.30±0.50; p<0.05). This significant difference was consistent both in the anterior and inferior myocardial infarctions (p<0.05). These findings demonstrate that intravenous streptokinase therapy is effective on limiting infarct size when given at the early stages of acute myocardial infarction.