This randomised controlled trial is a part of the ATACAS trial (Aspirin and Tranexamic Acid for Coronary Artery Surgery), to help answer whether aspirin should be stopped before coronary artery surgery. Only results regarding aspirin were presented in this paper. 1047 patients were randomly assigned to receive 100mg aspirin 1 to 2 hours before surgery and 1053 to receive placebo. The primary outcome was a composite of death and thrombotic complications (nonfatal myocardial infarction, stroke, pulmonary embolism, renal failure, or bowel infarction) within 30 days of surgery. There was no significant difference in the primary outcome events in aspirin (19.3%) vs placebo group (20.4%) (RR 0.94, 95% CI 0.80-1.12; P=0.55). There was also no difference in major haemorrhage events leading to reoperation (1.8% vs 2.1%, P=0.75) and cardiac tamponade rates (1.1% vs 0.4%, P=0.08) in the 2 groups.