The identification of unstable plaque is central in risk-stratifying patients for acute coronary events. Optical coherence tomography (OCT) is a recently introduced imaging modality that has shown considerable promise for the identification of high-risk plaques. Advantages of OCT include its high resolution (4 to 20 microm), high data acquisition rate, small and inexpensive guidewires/catheters, and ability to be combined with adjuvant optical techniques. This article summarizes the current state of intravascular OCT imaging, focusing on potential markers of instability and current limitations.