Objectives: To determine the incidence of early left ventricularinfarct expansion within five days after first anterior ST-segmentelevation myocardial infarction and the effect of early thrombolytictherapy on the incidence of early infarct expansion compared withlate thrombolytic therapy. Methods: In a prospective study of 101 patients (75males and26 females), with the first attack of acute anterior myocardialinfarction, their ages ranged from 40-80 years (mean age:61.07±10.78) who had been admitted to the Coronary CareUnit of Hawler Teaching Hospital for the period from July 2007through to September 2009. Those who received alteplase ≤3hours of acute myocardial infarction were labelled as group-I(49 patients) and those who received alteplase >3-12 hours werelabelled as group-II (52 patients). Results: The incidence of early left ventricular infarct expansionwas diagnosed by 2D-echocardiography and was found tobe 17.8%. Group I patients had a lower incidence of early leftventricular infarct expansion (8.16%) compared with group-II(26.92%; p=0.014). Patients with early left ventricular infarctexpansion had a higher frequency rate of left ventricular systolicdysfunction (94.44%) compared to patients without early leftventricular infarct expansion (8.43%; p<0.001). There was asignificant difference in the incidence of in-hospital mortalitybetween the patients who developed early left ventricular infarctexpansion (11.1%) compared with patients without early leftventricular infarct expansion (1.2%; p=0.025). Conclusion: Early reperfusion therapy in acute anteriormyocardial infarction can decrease the incidence of early leftventricular infarct expansion, preserve left ventricular systolicfunction and decrease in-hospital mortality.