Optical coherence tomography (OCT) is a recently developed technology capable of micron-scale imaging. Its high resolution (10-20 microm) makes intravascular OCT imaging the most interesting method for assessing atherosclerotic plaque microstructure in patients suffering from coronary artery disease. OCT allowed measurement of the thickness of the plaque fibrous cap, as well as identification of intima, media, and external elastic membrane in patients with normal coronary arteries. However, significant limitations still exist, including poor penetration in non-transparent tissue. The aim of this review is to give an update on OCT on the basis of the existing literature, with an overview of the strong and weak features of this technique.