Echocardiographic recording of the atrioventricular (AV) valve plane displacement was used for serial studies of left ventricular (LV) function in 27 patients with first-time acute myocardial infarction (MI) treated with a thrombolytic agent within 4 h of the onset of symptoms and showing noninvasive signs of early reperfusion. The recordings were made immediately before or during thrombolytic therapy and 24 h, 1 week, 1 month, and 2 months after attempted reperfusion. Regional LV function was assessed by recording the amplitude of systolic descent of the AV plane toward the apex at 4 different sites on left ventricle corresponding to the septal, anterior, lateral, and posterior walls from apical 4- and 2-chamber views. Global LV function was assessed using the mean value of the AV plane displacement from the above 4 sites (AV mean). In 15 patients with anterior MI, the displacement at the septum and anterior wall was significantly decreased compared with the posterior and lateral walls at baseline. The displacement had increased significantly after 1 week, 1 month, and 2 months (p less than 0.01, p less than 0.01, and p less than 0.001). The AV mean also increased significantly (p less than 0.01) during the study period. A corresponding regional increase was observed in inferior MI. The AV mean remained unchanged, however, during the follow-up period. It is concluded that the easy visualization and the simplicity of recording the AV plane displacement makes the method a valuable non-invasive tool for serial echocardiographic studies following acute MI treated with a thrombolytic agent.