Since January 1992 till June 1994, we experienced 22 cases of coronary revascularization (CABG) under hypothermic ventricular fibrillation (Vf) in patients with unclampable ascending aorta (Group 2). We compared them with patients undergoing conventional CABG with cardioplegic cardiac arrest (Group 1). All these 362 cases were primary isolated CABG. Comparing preoperative patient profile, patients of Group 2 were older (Group 1: 64.3 +/- 8.5, Group 2: 68.2 +/- 6.7 year old, p < 0.05), had more unstable angina (Group 1: 20.3%, Group 2: 54.5%, p < 0.001), and had more severe NYHA classification (Group 1: 2.22 +/- 0.55, Group 2: 2.73 +/- 0.46, p < 0.05) than Group 1. There were no significant difference between both groups about other factors. Comparing post operative complication, low output syndrome (Group 1: 2.6%, Group 2: 18.2%, p < 0.005) perioperative myocardial infarction (PMI) (Group 1: 4.4%, Group 2: 36.4%, p < 0.0001) ventricular tachycardia (VT) (Group 1: 1.4%, Group 2: 18.2%, p < 0.0001), respiratory failure (Group 1: 3.8%, Group 2: 18.2%, p < 0.005), and post operative hospital death (Group 1: 2.9%, Group 2: 18.2%, p < 0.0005) occurred more frequent in Group 2 than Group 1. Other complication (renal failure, wound infection, cerebrovascular accident, rethoracotomy for bleeding) equally occurred in both groups. Long Vf time (mean 92.8 minutes) and low perfusion pressure during Vf (mean 60.0 mmHg) were suspected to be major cause of high incidence of PMI and VT in Group 2. But there were no correlation between Vf time, perfusion pressure and occurrence of PMI and/or VT.(ABSTRACT TRUNCATED AT 250 WORDS)