BACKGROUND: Coronary artery disease (CAD) is narrowing of the coronary artery due to atherosclerosis. Surgery with or without cardiopulmonary bypass plays a key role in the treatment of obstructive CAD and the benefit of one technique over the other has been a contentious topic of discuss. Post operative renal dysfunction is relatively common and one of the serious complications of cardiac surgery3. Renal dysfunction or failure occurs in about 8% of all patients undergoing myocardial revascularization. Its aetiology is multi-factorial. Each year about six hundred thousand patients worldwide undergo coronary artery bypass graft (CABG) surgery. In the centre where this study was conducted, both techniques are practiced and this study found both techniques as viable options in selected patients. AIMS: To compare the risk of acute renal dysfunction after first isolated Off-pump versus On-pump coronary artery by-pass surgery and to determine if there is a difference between the two groups. METHODOLOGY: This was a prospective observational study of acute renal dysfunction in patients after first isolated off-pump versus on-pump coronary bypass graft surgery. After institutional clearance, patient’s demography, preoperative and post-operative serum creatinine and other blood investigations were recorded in a proforma designed for the study. Patients with preoperative serum creatinine greater than 1mg/dl as well as those having combined CABG and valve surgery or emergency surgery were excluded. RESULTS: From June 2015 to June 2016 a total of 288 patients had CABG surgery at the Heart Medanta Hospital, New Delhi, India. One hundred and fifty four patients had Off-pump CABG while 134 had On-pump CABG. Eighty seven percent (87%) were male while 12% were female. Of those who had Off-pump CABG, 137(89%) were male while 17(11%) were female. One hundred and fifteen (85%) male and 19 (14%) of female had On-pump CABG. There was a steady rise in creatinine from the preoperative mean baseline of 0.8mg/dl for both groups starting from 24 hours postoperative period, peaking to 1.2mg/dl and 0.81mg/dl by 48 hours for the on-pump and off-pump groups respectively and dropping to 0.84mg/dl and 0.73mg/dl for the on pump and off-pump respectively by one week. A critical analysis of the creatinine pattern for each group showed that for patients who had off-pump CABG, the creatinine showed an average rise of 0.01mg/dl from base line compared to patients who had on-pump CABG in which there was a significant average rise in creatinine of 0.4mg/dl from preoperative values. CONCLUSION: This study has shown that on-pump CABG causes significant renal dysfunction compared to off-pump coronary artery bypass surgery. A longer period of follow up is however, suggested as this might reveal more characteristics of the two groups. Key words: Acute renal dysfunction, On-pump CABG, Off-pump CABG.