Intravascular ultrasound imaging provides a direct view of atherosclerotic disease, generating in vivo information about the depth and mechanical characteristics of plaque at any point in the vessel wall. For this reason, ultrasound has significant potential to serve as a guidance modality for catheter-based techniques designed to remove or ablate plaque. Although the current generation mechanical atherectomy, laser ablation and ultrasound pulverization techniques all have some specificity for attacking plaque as opposed to normal vessel wall, it appears that in practice all of these devices will continue to carry a risk of traumatizing or even perforating arteries. In addition, it seems highly likely that aggressive 'debulking' of plaque will require some type of guidance beyond angiography - a role which ultrasound is theoretically well suited to play. The purpose of this review is to consider the theoretical and practical applications of ultrasound imaging as a guide to catheter-based plaque removal and ablation techniques. Specific uses will be discussed with respect to both directional and coaxial therapeutic devices.