Intravascular ultrasound (IVUS) provides high-resolution vessel imaging and has been shown to improve clinical outcomes when used to assess the technical result of peripheral angioplasty procedures. Our vascular group compared anatomic and clinical outcomes of carotid artery stent-angioplasty (CAS) performed with angiogram monitoring alone, or in combination with IVUS imaging to select stent/balloon diameter and interrogate stent deployment region for residual stenosis. A retrospective review of our carotid stent registry (N=306) identified 220 CAS procedures performed with either a digital C-arm fluoroscopy alone (N=110) or in conjunction with IVUS (N=110) with at least 6-month of clinical follow-up. Outcome measures of procedure time, angioplasty balloon diameter, contrast dye volume, Duplex surveillance testing for recurrent stenosis, and procedure event (death, cardiac, neurologic) rates were compared to assess the risks and benefits of IVUS. All procedures utilized a cerebral protection device deployed prior to IVUS imaging. Procedure times were similar, but IVUS usage resulted in lower (P<0.05) contrast agent volumes due to fewer angiogram runs for stent sizing and verification of adequate stent deployment. IVUS imaging resulted in the use of larger diameter balloons (typically 6 mm) for final stent angioplasty based on distal internal carotid artery (ICA) dia measurements, and identified (P<0.01) more residual stent abnormalities (N=12, 11%) versus CAS with angiogram assessment alone (N=2, 1.8%). No procedural or 30-day cardiac events or deaths occurred. The overall stroke rate was 0.9%; two events (stroke-1; reperfusion injury-1) in the angio+IVUS group (1.8%) and none in the angio alone group. Duplex ultrasound surveillance following CAS demonstrated a higher (P<0.01) incidence of >50% diameter-reducing in-stent stenosis in the angio alone group (11% vs 7% at 1 month ; 24% vs 6% at last surveillance; mean 36 moontha; range: 6-66 months). The quality control of the CAS procedure was enhanced by IVUS imaging which directed stent /balloon sizing and was more accurate than angiography in confirming adequate stent expansion. No IVUS related adverse events occurred. Based on the anatomic information provided by IVUS, larger diameter angioplasty balloons were used which correlated with less residual stenosis after CAS based on duplex ultrasound testing.