The effect of antiplatelet therapy (APT) on postoperative bleeding, transfusion needs and re-exploration remains unclear. This study examines the influence of APT, as well as antiplatelet mono- and combined therapy, on haemorrhage and transfusion requirements in patients undergoing coronary artery bypass on cardiopulmonary bypass (CPB). Six hundred and fifty patients were reviewed retrospectively, 325 patients received APT within seven days and 325 control patients. APT group had two subgroups: clopidogrel (CLO) group: n=48 patients received CLO as mono-therapy; combined group: n=277 patients received both CLO and aspirin (ASS). The mediastinal drainage at 12 h was control group: 505 ml+/-445 ml and APT group: 802 ml+/-720 ml, P<0.001. APT group (vs. control group) received significantly more units of blood (3.9+/-4.2 vs. 1.9+/-2.6; P<0.001), platelet units (1.0+/-1.4 vs. 0.1+/-0.3; P<0.001), and fresh frozen plasma (FFP) units (2.9+/-3.9 vs. 0.9+/-2.2; P<0.001), respectively. Combined and mono-therapy groups had no significant differences in bleeding and blood transfusion. Considerations should be given to delaying elective coronary surgery for patients received APT for seven days.