Optical coherence tomography (OCT) is a new imaging technology that utilizes advanced photonics and fiberoptics to obtain images and tissue characterization on a microscopic scale. The resolution of the current OCT system is 10-20 microm, which is approximately ten-times higher than that of intravascular ultrasound. Compared with conventional imaging modalities, OCT has a superior ability to evaluate vulnerable plaque features, such as plaque rupture, intracoronary thrombus, thin-capped fibroatheroma and macrophages within the fibrous caps. Furthermore, OCT can clearly visualize stent malapposition and tissue protrusion after stenting and neointimal hyperplasia at late follow-up. Although OCT is a specialized research tool, it might provide new insights into the diagnosis and treatment of coronary artery disease.