In patients undergoing coronary artery bypass graft (CAGB) surgery, aspirin is commonly prescribed to prevent graft thrombosis and myocardial ischemia. However, there are still a significant number of grafts occluding in the postoperative period. This is partly attributed to reduced aspirin responsiveness, also called "aspirin resistance". At the moment, no standardized definition or laboratory test is available to quantify "aspirin resistance", and strong platelet reactivity in laboratory tests is not necessarily associated with increased thrombotic events. However, there is increasing evidence that reduced aspirin responsiveness in platelet function analyzers is associated with adverse long-term outcome and higher incidence of major adverse events in patients with stable coronary artery disease and in patients undergoing percutaneous coronary intervention. In patients undergoing coronary artery bypass graft surgery, the predictive value of a laboratory finding of reduced aspirin responsiveness remains unclear.