for the AVID InvestigatorsBackground-AVID (Angiography Versus Intravascular ultrasound-Directed stent placement) is a multicenter, randomized controlled trial designed to assess the effect of intravascular ultrasound (IVUS)-directed stent placement on the 12-month rate of target lesion revascularization (TLR). Methods and Results-After elective coronary stent placement and an optimal angiographic result (Ͻ10% stenosis), 800 patients were randomized to Angiography-or IVUS-directed therapy. Blinded IVUS was performed in the Angiography group without further therapy. In the IVUS group, IVUS criteria for optimal stent placement (Ͻ10% area stenosis, apposition, and absence of dissection) were applied. Final minimum stent area was 6.90Ϯ2.43 mm 2 in the Angiography group and 7.55Ϯ2.82 mm 2 in the IVUS group (Pϭ0.001). In the IVUS group, only 37% with inadequate expansion (Ͻ90%) received further therapy. The 12-month TLR rate was 12.0% in the Angiography group and 8.1% in the IVUS group (Pϭ0.08, 95% confidence level [CI], [Ϫ8.3% to 0.5%]). When vessels with a distal reference diameter Ͻ2.5 mm by core laboratory angiography measurement were excluded from analysis, the 12-month TLR rate was 10.1% in the Angiography group and 4.3% in the IVUS group (Pϭ0.01, 95% CI, [Ϫ10.6% to Ϫ1.2%]). With a prestent angiographic stenosis of Ն70%, the TLR rate was lower in the IVUS group compared with the Angiography group (3.1% versus 14.2%; Pϭ0.002; 95% CI, [Ϫ18.4% to Ϫ4.2%]). Conclusions-IVUS-directed bare-metal stent placement results in larger acute stent dimensions without an increase in complications and a significantly lower 12-month TLR rate for vessels Ն2.5 mm by angiography and for vessels with high-grade prestent stenosis. However, for the entire sample analyzed on an intention-to-treat basis, IVUS-directed bare-metal stent placement does not significantly reduce the 12-month TLR rate when compared with stent placement guided by angiography alone. In addition, IVUS evaluation of adequate stent expansion is underutilized by experienced operators. (Circ Cardiovasc Intervent. 2009;2:113-123.)