Essential thrombocythemia (ET) can cause systemic vascular thrombosis but rarely cause obstruction of coronary arteries or acute myocardial infarction (MI). Treatment of acute MI in patients with ET may be a problem due to the important role of platelets in the pathogenesis of infarction. In this report, a 63-year-old man presented with acute chest pain and a greatly increased platelet count. The patient was successfully treated with intravenous tirofiban, a glycoprotein IIb/IIIa receptor blocker. Essential thrombocythemia was diagnosed based on bone marrow findings, clinical presentation, and laboratory analysis. Thrombocythemia had been controlled with hydroxyurea.