Background and objectives: Although both on-pump and off-pump techniques have been used to aid coronary revascularization, the group of high risk patients needs special attention regarding which technique provides the best outcome. We hypothesized that coronary artery bypass grafting in high risk patients using both techniques, would have nearly the same early postoperative outcome. The aim of the study was to evaluate and compare advantages and disadvantages of on-pump technique in comparison with the off-pump one in high-risk ischemic heart disease patients. Methodology: Fifty patients with ischemic heart disease were considered to be high risk for having either an ejection fraction (EF) of <35%, or left main disease >75%, or unstable angina will be randomized into two groups, group "A" will undergo coronary revascularization using the on-pump technique. Group "B" will undergo coronary revascularization using the Off-pump (OPCAB) technique. The mean age for group "A" was 56.7±3.7 with a range of 46-63 years. The mean age for group "B" was 58.3±4.2 with a range of 45-67 years. Group "A" had 52% of patients with EF <35%, 24% with left main disease >75% and 24% with unstable angina. In group "B", there were 40% of patients with EF <35%, 32% with left main disease >75% and 28% with unstable angina. Results: There was no statistical difference between the two groups preoperatively regarding their age, sex, Canadian cardiovascular society angina classification, comorbidities and left ventricular function. There was a single operative mortality in each group, and non significant difference in postoperative complications. Total hospital stay, ICU stay, operation time, postoperative bleeding, blood transfusion, ventilator support were less in group "B", while the total number of grafts received were more in group "A". Conclusion: Avoidance of cardiopulmonary bypass does not confer significant clinical advantages in all high risk coronary patients; instead, there are particular subsets of patients in whom beating heart surgery can be particularly indicated and others for whom on-pump revascularization appears a better solution. Adaptation of the operation to the single patient is probably the way to improve outcome.