Antithrombotic therapy, including antiplatelet and antithrombin agents, effectively reduces the risk of ischemic events in patients with acute coronary syndromes (ACS) and those undergoing percutaneous coronary intervention (PCI). Unfortunately, these agents intrinsically increase the risk of bleeding complications, which in turn are associated with adverse outcomes, particularly mortality. Accordingly, there is great value in improving the understanding of bleeding complications, including the definitions employed, severity and types of bleeding, as well as the patient characteristics, clinical presentations, and treatment variables that are associated with an increased risk of bleeding. The ultimate goal is to optimize patient outcomes by employing pharmacological and nonpharmacological strategies that minimize bleeding risk while maintaining efficacy. The objective of this article is to present the criteria by which bleeding is expressed and discuss the correlation between bleeding and adverse outcomes, as well as the relative impact of bleeding compared with ischemic events such as myocardial infarction on mortality. Furthermore, the relationship between bleeding and modifications of long-term treatment and methods to predict and prevent bleeding will be explored.