Obstruction of the coronary microvasculature contributes to the pathophysiology of MI and adversely affects post-MI recovery. This "no-reflow" phenomenon resulting from microvascular obstruction is an indicator of lack of adequate tissue perfusion within the infarcted myocardium, even after restoration of epicardial blood flow. Regions of microvascular obstruction can be detected and quantifed because of rapid advances in and refinement of imaging technologies over the past decade. This article focuses on the non-invasive imaging modalities used to assess MO, discusses the prognostic implications of MO, and briefly addresses strategies for reducing MO.