Acute myocardial infarction results in not only left ventricular but also left atrial dysfunction. Left atrial function is important for optimal filling of the left ventricle. In this study, we aimed at evaluating left atrial functions 6 months after acute myocardial infarction in three different patient groups (thrombolytic therapy, primary percutaneous intervention, or no reperfusion strategies). Between October 2002 and May 2003, 48 patients with ST elevation myocardial infarction who were either administered thrombolytic therapy (group T, n=16), underwent primary angioplasty (group A, n=20), or underwent no reperfusion therapy (group C, n=12) at our unit were enrolled into the study. Echocardiography was performed in these patients 6 months after acute myocardial infarction. Left atrial contractility was assessed by atrial ejection force. Left atrial contribution was assessed by atrial fractional shortening and left atrial volume was calculated. The left atrial volume was significantly higher in group C (P<0.05), but there was no significant difference between groups A and T (P>0.05). Patients in group C had significantly lower atrial ejection force values compared with the other groups (P<0.05). Atrial fractional shortening was not significantly different among the three groups (P>0.05). Atrial ejection force, which is an indicator of left atrial contractility, is better with either angioplasty or thrombolysis. Left atrial volume is higher in patients who were not treated with reperfusion strategies. Further studies are needed to explain the mechanism involved.