Operative transluminal coronary artery balloon angioplasty has been used for over 3000 lesions in 1000 patients since 1980. Initially it was only used for distal stenoses not accessible to coronary bypass grafting in 200 patients. Recatheterization of patients who had intraoperative transluminal balloon angioplasty of the proximal left anterior descending, right, and circumflex coronary arteries 3 years previously revealed excellent patency of both the bypass grafts and the dilated native coronary arteries. This observation supports the thesis that with properly constructed bypass anastomoses competitive flow does not significantly mandate graft thrombosis. Subsequently, intraoperative balloon angioplasty has been performed for both proximal and distal stenoses in 800 patients to improve native coronary artery perfusion and maximize revascularization. Follow-up from 1 to 7 years revealed perioperative myocardial infarction in 21 patients (2.1%) and death in 19 patients (1.9%). Recatheterization from 1 to 7 years after the operation in 51 patients (41 with symptoms) revealed that patency was almost as prevalent in arteries subjected to angioplasty (82%; 137/167) as in bypass grafts (84%; 102/122). Intraoperative balloon angioplasty appears to improve coronary artery perfusion without detrimental competitive flow when used with bypass grafts.