Background This study compares the outcome of percutaneous coronary interventions (PCI) with bilateral internal thoracic grafting (BITA) in diabetic patients. Methods From May 1996 to December 1999, 802 consecutive diabetic patients underwent myocardial revascularization: 363 by PCI and 439 by BITA. The two groups were similar; however, left main disease (28% versus 3.3%), ejection fraction less than 0.35 (14.5% versus 5.5%), and chronic obstructive lung disease (8.4% versus 3%) were more prevalent in the BITA group, and prior percutaneous transluminal coronary angioplasty, in the PCI group (16.8% versus 10.5%). Results The number of coronary vessels treated per patient was higher in the BITA group (3.4 versus 1.2; p < 0.001). Thirty-day mortality was similar: 3.4% in the BITA group and 2.8% in the PCI group. Late follow-up (3 to 6.5 years) showed decreased return of angina (11% versus 64%; p < 0.001), fewer reinterventions (2.7% versus 55%; p < 0.001), and increased cardiovascular event-free survival (80% versus 30%; p < 0.001) in the BITA group. Six-year survival of BITA and PCI patients was 85.5% and 81.2%, respectively (not significant). However, survival of the subgroups of patients with left main or three-vessel coronary artery disease was significantly better with BITA (86% versus 76%; p = 0.003). Conclusions Despite higher risk profile of diabetic patients treated surgically by BITA, their late outcome is better than that of patients treated by PCI. The results of this study support referring diabetics with single-vessel or double-vessel disease to PCI and those with three-vessel and left main coronary artery disease to surgery.