Aims: The aim of this study was to assess the expansion capacity of current commercially available Drug Eluting Stents (DES) with nominal diameters of 3.5-4.0mm in patients with Left Main disease. Materials and Methods: This study was conducted on 50 Patients who underwent percutaneous coronary intervention (PCI)for Left Main disease at Benha university hospitals and National Heart Institute. PCI was done with Drug Eluting Stents (DES) with large diameters of 3.5-4mm and post dilatation was done with non-compliant (NC) balloons with diameters of 4.5- 5mm. Intravascular ultrasound (IVUS) was used to measure maximal stent diameter and area. Results: Three commercially available DESs were used in our study; XIENCE Xpeditionᵀᴹ, Ultimasterᵀᴹ and Onyxᵀᴹ. Maximal stent diameter was 4.5±0.3mm and diameter expansion index was 0.96±0.05. Maximal stent area was 14.67±2.06mm² and area expansion index was 0.86±0.07mm². On IVUS images, significantly more calcification< 90 ̊ was detected in the group with expansion index ˂ 0.85 (68.4 percent versus 25.8%, P=0.003) compared to the group with expansion index >0.85. We found that DESs with diameters of 3.5-4.0mm can be expanded up to diameter of 5.3mm after post-dilation. No complications were reported in the studied patients, including perforation or stent fracture. Conclusion: Current DESs with nominal diameters of 3.5-4.0mm can be safely and effectively over-expanded to reach the predicted diameters in the left main, but the presence of calcification >90 may affect the achievement of the predicted area.