Dual antiplatelet therapy (DAPT) including aspirin and a P2Y12 inhibitor is the cornerstone for the treatment of patients with acute coronary syndrome (ACS). The introduction of more potent drugs significantly reduced ischemic events, but with an associated increased risk of bleeding. Although appropriate estimation of bleeding risk by comparing the single drugs is challenging, mainly because of differences in definitions, it has been consistently shown that bleeding events are associated with an adverse outcome, both at short and long-term follow-up.Current guidelines recommend a short DAPT in patients at high bleeding risk, making appropriate risk estimation of crucial importance. Several numerical scores have been proposed for use in daily clinical practice. Although an objective risk assessment provides superior risk discrimination compared to physician's estimation, none of these scores appear free from limitations, nor have been obtained from cohorts of patients on short-tern treatment with prasugrel or ticagrelor. In the present review, we report the rates of major bleeding observed in the main randomized clinical trials and registries, their association with mortality, differences in definitions when used as safety endpoint, and finally the scores currently used for evaluation in daily clinical practice.