During the last several years, major improvements in intravascular ultrasound image quality have led to new and important information about the clinical application of rotational atherectomy. Ultrasound is providing data on the mechanism of luman enlargement, burr sizing, and the effects of the procedure on different plaque morphologies. This information is often important for optimizing device selection and procedural success, as well as for minimizing complications. In this review we first discuss the currently available data regarding the mechanisms of lumen enlargement following rotational ablation and the implications of these findings for lesion and patient selection. We review how this data is modifying several of the technical aspects of the rotational ablation procedure in the interventional laboratory. We than assess the available data that suggest that preprocedural ultrasound examination may eventually help to identify lesions at high risk for adverse outcome with stand-alone balloon angioplasty or stent placement. These ultrasound data may help triage many of these targets to initial debulking with rotational ablation. Finally, we review data that suggest that ultrasound analysis has important implications for comparative trials of new devices, particularly trials of the Rotabalator.