A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether early administration of aspirin might optimize vein graft patency. More than 250 papers were found using the reported search, of which 4 new papers in addition to the previous 7 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Early postoperative aspirin administered within 6 h following coronary artery bypass grafting (CABG) has been shown to be optimal for prevention of vein graft occlusion. Early aspirin has significant benefit in reducing vein graft occlusion, mortality, myocardial infarction, stroke, renal failure and bowel infarction. The efficacy of early postoperative aspirin on vein graft patency diminishes the later it is administered. It has optimal benefit at 6 h, some benefit at 24 h and no benefit after 48 h post CABG. ACC/AHA, EACTS and ACCP have issued guidelines recommending administration of early aspirin or an alternative (clopidogrel, ticlopidine and indobufen) at 6 h or soon after bleeding has settled as the standard of care for optimization of vein graft patency. The ACCP guideline has also suggested that optimal prevention of cardiovascular complication should have higher value than prevention of postoperative bleeding. Several randomized, controlled studies, including a meta-analysis, have shown that early administration of aspirin following CABG is not associated with increased blood loss or transfusion requirement. Postoperative bleeding has been identified as a significant reason for non administration of early aspirin in a prospective study. It is essential to define/quantify the postoperative blood loss that precludes administration of early aspirin. This will enhance prompt administration in some cases and guide judgement, especially in patients with high-risk factors for vein graft thrombosis. Administration at 6 h is the optimal time to give aspirin as long as bleeding has settled.