Over the last 50 years the introduction of several imaging technologies have been pivotal in reducing mortality associated with coronary artery disease. However coronary disease continues to be the leading cause of mortality in the industrialized world. Optical coherence tomography (OCT) has recently been introduced for micron scale intravascular imaging. It is analogous to ultrasound, measuring the intensity of back-reflected infrared light instead of sound. Some of the advantages of OCT include its resolution, which is higher than any currently available imaging technology and acquisition rates are near video speed. Unlike ultrasound, OCT catheters consist of simple fiber optics and contain no transducers within their frame, thereby making imaging catheters both inexpensive and small. Currently, the smallest catheters have a cross-sectional diameter of 0.014". OCT systems are compact and portable and can be combined with a range of spectroscopic techniques. We review the application of OCT to intracoronary imaging.