Larger final lumen dimensions after percutaneous coronary interventions in native coronary arteries lead to lower restenosis rates. We sought to determine the impact of stent expansion, as assessed by intravascular ultrasound, on clinical results of stent implantation in saphenous vein grafts (SVGs). We identified 226 consecutive patients who underwent intravascular ultrasound-guided stenting of 234 de novo SVG lesions. Patients were divided into 2 groups based on the final stent cross-sectional area (CSA): group I (stent CSA <100% of the reference lumen CSA, n = 176 patients, 182 lesions) and group II (stent CSA >/=100% of the reference lumen CSA, n = 50 patients, 52 lesions). Baseline patient characteristics were similar between the 2 groups with the exception of smaller lesions in group II. More aggressive stent expansion (group II) was associated with (1) increased rates of in-hospital non-Q-wave myocardial infarction (29% vs 17%, p = 0.05), (2) any myocardial infarction (26% vs 8%, p = 0.003) at 1-year follow-up, and (3) no improvement in target vessel revascularization at 1 year (31% vs 26%, p = 0.3). Aggressive stent expansion in SVG lesions resulted in higher myocardial infarction rates and, unlike native arteries, no improvement in target vessel revascularization rate at 1 year. A less aggressive stent implantation strategy in SVGs than in native coronary lesions appears prudent.