High resolution imaging of intraarterial structure is necessary for the identification of high risk coronary plaque. Optical Coherence Tomography (OCT), a recently developed technology, is a compact, fiber optic based imaging modality with resolutions between 2 - 20 μm and real time image acquisition rates. Previous in vitro studies have demonstrated the capability of OCT to identify plaque morphology and distinguish plaques with high lipid content. This work demonstrates the feasibility for OCT imaging of in-vivo intraarterial structures. We demonstrate the detection of microstructural detail and the effects of blood on imaging. Saline injections were required during imaging to reduce the signal attenuation of blood. An axial resolution of 10 μm was achieved. Microstructure within the arterial wall was sharply defined and correlated with histology. OCT shows potential to assist in the risk stratification of plaques and the guidance of interventional procedures, such as stent deployment.