The background use of a number of established therapies presents a key challenge for the development of novel anti-atherosclerotic agents: how to predict potential efficacy before the completion of long-term trials with endpoints such as mortality. This challenge has stimulated the search to develop intermediate measures of efficacy. Recent advances now allow intravascular ultrasound (IVUS) to provide an accurate assessment of atheroma accumulation within the arterial wall. Here we describe how IVUS can be applied to the serial assessment of atheroma burden in response to treatment with a range of anti-atherosclerotic strategies, which has resulted in its emergence as a key technology in the evaluation and approval of novel drugs.