Antithrombotic therapy and invasive risk stratification in selected high-risk patients have improved outcomes from non-ST-segment elevation acute coronary syndromes (NSTE-ACS), but carry a risk of bleeding and blood transfusion. Although the true incidence of bleeding depends on the population studied (i.e. clinical trial vs. registry), the definition used, and the use of invasive procedures, it is becoming clear that bleeding is associated with an increased risk for adverse outcomes including myocardial infarction and death. Blood transfusion itself may carry a risk for ischaemic outcomes that is independent of bleeding. Therefore, therapies that provide an adequate level of anticoagulation to reduce ischaemia while simultaneously minimizing the risk of bleeding and transfusion have the potential to improve outcomes among patients with NSTE-ACS. Anticoagulants studied in recent clinical trials that have focused on bleeding reduction include fondaparinux and bivalirudin. In this review, we discuss the clinical trial evidence for these agents, the association between bleeding and clinical outcomes, the biology of blood transfusion and potential mechanisms underlying its association with adverse outcomes, and propose strategies to deal with bleeding complications. Future directions for research and clinical practice are also discussed.