Background: We have performed off-pump coronary artery bypass grafting and also performed early postoperative angiography to assess anastomosis accuracy and patency in most of our patients requiring surgical revascularization. Methods: Of 3083 patients who underwent isolated coronary artery bypass grafting between 1998 and 2017, 2919 patients (94.7%) underwent off-pump coronary artery bypass grafting. Conduits for distal anastomoses were left internal thoracic artery (n = 2764), right internal thoracic artery (n = 866), right gastroepiploic artery (n = 997), radial artery (n = 16), and saphenous vein (n = 1505). Since the introduction of transit-time flow measurement in 2000, we revised abnormal grafts intraoperatively. Early (≤7 days) angiography was performed in 2820 patients (96.6%) at 1.5 ± 1.2 postoperative days, and surgical intervention was performed based on angiographic findings. Results: Operative mortality was 1.1% (32 of 2919). Average number of distal anastomoses was 3.2 ± 1.0. Intraoperative flowmetry-guided revision for distal anastomosis failures was performed in 109 of 8585 distal anastomoses (1.3%). Angiography showed an overall patency of 98.2% (8836 of 9001): 99.0% (5484 of 5540) for arterial and 96.9% (3352 of 3461) for venous conduits (P < .001). Patency of venous conduits was 87.2% (231 of 265) for free grafts and 97.7% (3121 of 3196) for composite grafts (P = .001). After the introduction of transit-time flow measurement, patency of arterial conduits became significantly higher (97.2% vs 99.2%; P = .038); however, patency of free venous conduits was not significantly improved (86.0% vs 91.4%; P = .181). Early re-intervention according to angiographic findings was performed in 76 patients (2.7%). Reevaluation of graft patency before discharge in 31 who underwent revision of distal anastomoses showed improved patency (65.1% [56 of 86] vs 95.3% [82 of 86]; P < .001). Conclusions: Intraoperative flowmetry and revision of abnormal grafts improved early arterial graft patency, and reoperation based on early angiographic findings may further improve graft patency at the time of discharge.