Objective: The use of preoperative inta-aortic balloon pump (IABP) can reduce perioperative myocardial ischaemia and thus improve outcome in high risk patients undergoing coronary artery bypass operations with the use of cardiopulmonary bypass (CPB). The aim was to evaluate the efficacy of preoperative IABP treatment on perioperative and postoperative cardiac performance, mortality and morbidity, and the optimal timing for its insertion. Patients and Methods: Between 2006 and 2011, 48 high risk patients with coronary artery disease underwent CABG. The mean age was 62±6 years. The patients presented with at least two or more of the following criteria: left main coronary artery stenosis was ≥70%, left ventricular ejection fraction was ≤40%, and unstable angina despite of medical treatment. Patients not fulfilling these high risk criteria were not included in the study as well as those with cardiogenic shock preoperatively. The patients were randomized into 3 groups, group 1 (n=11 patients) received IABP treatment for 24 hours before surgery, group 2 (n=16 patients) received IABP treatment for 1-2 hours before surgery, group 3 (n=21 patients) didn't receive IABP preoperatively. Group 1 and 2 were chosen to evaluate the best timing for preoperative IABP.