BACKGROUND: This study was performed to determine the size of left ventricular thrombus (LVT), risk of systemic embolization and response to medical treatment during 18 months of follow up in the patients with anterior-ST elevation myocardial infarction (aSTEMI). METHODS: This cross-sectional study was performed on thirty-five patients with anterior myocardial infarction (MI), in Emam Reza Hospital and Ghaem Hospital, Mashhad, Iran, from August 2008 to January 2011. Warfarin was prescribed for all the patients. Transthoracic echocardiographic study was performed on the 1st, 2nd, 4th, 6th, 12th and 18th months. Outcomes included rate of death, MI, stroke, systemic embolization, major bleeding and change in thrombus size following treatment. RESULTS: The resolve rate of clot on the 2nd, 4th, 6th, 12th and 18th months was 64.7, 86.6, 81.4, 81.4 and 100 percent, respectively. In five patients with complete clot resolution, clot reformation occurred after warfarin discontinuation. In these patients, left ventricular ejection fraction (LVEF) improvement was poor. During the study period, five patients died due to severe heart failure. One patient developed hematuria whereas non-experienced thromboembolic events. The mean LVEF at study initiation was 30.8 ± 0.92%, which improved to 42 ± 0.84% (P < 0.05) at the end. CONCLUSION: All LVT was resolved with a combination therapy of antiplatelet and warfarin without any thromboembolic event. In patients with a poor improvement in the LV function, due to the risk of LVT reformation, lifelong warfarin therapy was recommended.