All efforts are focused on reducing the length of coronary blockage and myocardial ischemia in order to lessen myocardial necrosis in the era of prompt reperfusion for patients with acute myocardial infarction. Despite all these efforts, there is still a residual risk of myocardial ischemia which emerged under the title of no-reflow phenomenon. No-reflow phenomenon represents myocardium hypoperfusion in the setting of a patent epicardial coronary artery. It is usually backed to microvascular obstruction, which may be produced by various mechanisms. This article aimed to review clinical Impact, diagnosis, and the possible management of No-reflow phenomenon.