Determining the severity of intermediate coronary artery lesions is a clinical dilemma. Physiologic assessment of these lesions can establish the presence of ischemia to justify percutaneous coronary intervention (PCI). Approximately 50% of patients undergo PCI without any noninvasive, cardiac, function testing to assess for myocardial ischemia. Intravascular ultrasound (IVUS) is a highresolution, tomographic imaging modality used to identify vessel size, morphology, and its subsequent layers. The use of IVUS continues to evolve with applications in understanding plaque composition and burden, determination of reference diameter and appropriate stent placement after PCI, assessment for cardiac allograft vasculopathy after cardiac transplantation, and possible identification of vulnerable plaques which may lead to future coronary events. We review the literature related to the use of IVUS in intermediate, non-left main lesions of the coronary vasculature and its correlation with fractional flow reserve (FFR). Given the paucity of randomized controlled clinical trials in this area, it is difficult to make conclusions regarding the best cutoff value for IVUS which may correlate to ischemia producing lesions.