This best evidence topic was investigated according to a described protocol. The question asked was: should patients on acetylsalicylic acid (ASA) for secondary prevention stop or continue the medication prior to elective, abdominal surgery. Using the reported search 826 papers were found of which five represented the best evidence to answer the clinical question. The strongest evidence was from a randomized controlled trial (RCT) specifically looking at elective abdominal surgery, which showed no statistically significant difference between ASA continuation and discontinuation in terms of haemorrhagic or thrombotic events. Two other RCT's examined elective non-cardiac surgery but only a minor proportion (20.6% and 23.6%) of patients underwent abdominal surgery and data were unavailable regarding adverse events in these patients. However, one of these trials did show a 7.2% absolute risk reduction in postoperative cardiac adverse events when ASA was continued. One prospective cohort study found no difference between ASA maintenance and cessation except for longer duration of surgery in the ASA continuation group. Finally one recent retrospective cohort study revealed similar bleeding rates between ASA-treated and non-ASA-treated patients but increased cardiac complication rates in the ASA group. Only two studies compared continuation versus discontinuation of ASA, while the remaining three looked at patients on ASA versus those not on ASA. This heterogeneity in methodology makes it difficult to draw justifiable conclusions from the data. However, it appears that continuing ASA isn't associated with excessive bleeding. Further adequately powered trials with well-defined end points are needed to answer this important clinical question.