Background:Coronary artery disease is higher in risk with diabetes mellitus, and diabetesrelated deaths can lead to ischemic heart disease. We examined the relationship between the glycemic regulation as determined by Hemoglobin A1c and the occurrence of periprocedural complications in patients who performed percutaneous coronary intervention (PCI) and had Coronary artery Bypass Graft (CABG) Objective: To identify associated complications and their sites with Percutaneous Coronary Intervention in diabetic patientswho performed Coronary Artery Bypass Graft. Methods:The cross-sectional analysis was performed at the cardiology department in Zagazig University Hospital in which all 24 CABG & DM patients were included during the period between January 2019 and January 2020 divided into 12 patients with controlled DM(HbA1c>7)&12 patients with uncontrolled DM (HbA1c<7).Both patients had a complete medical history, a detailed clinical evaluation, and preoperative laboratory work: role of the renal, completion of blood counts as a marker for regulation of DM, ECG, and ECHO. Glycosylated Hemoglobin HbA1c was used. Results:There was a statistically non-significant increase in PCI of Native coronaries in group 2 compared to group 1 (p=0.386) and also there was a statistically non-significant increase in PCI of Vein graft in group 2 compared to group 1 (p=0.371) but There was a statistically nonsignificant increase in PCI of Arterial in group 1compared to group 2 (p=0.217)). There was no statistically significant difference between the two groups (p=0.131).Rate of failure of venous graft PCI in uncontrolled diabetes was much higher than in those with controlled diabetes (83% compared to 50% respectively). Conclusion:Control of DM guided by HbA1c level (<7) reduces the complications during percutaneous coronary intervention in diabetic patients with a previous coronary artery bypass graft. And in these patients who need elective PCI, control of their diabetes is advised before the procedure.In cases of uncontrolled diabetes, it is preferred to use arterial Graft instead of venous Graft in Bypass Graft Procedure. 2163