No reflow occurs when there is inadequate myocardial perfusion of a given segment of the coronary circulation without evidence of epicardial vessel obstruction. It is a rare but clinically significant condition associated with myocardial infarction and coronary interventions. Diagnosis is usually based on clinical signs of myocardial ischemia (symptoms and/or ECG changes) combined with coronary angiography. Management can be difficult and primarily consists of intracoronary administration of vasodilators. One interesting etiology is thromboembolism and this has become the focus for new potential treatments, including distal embolic protection devices.