Several endoscopic imaging techniques such as magnification endoscopy, narrowband imaging (NBI) and chromoendoscopy have been developed to enhance visualization of GI pathology, but can have limited sensitivity and specificity. Endoscopic Optical Coherence Tomography (OCT) performs volumetric imaging with near-microscopic resolution, however, with commercial endoscopic OCT systems visualization is mainly limited to cross-sectional imaging planes owing to limitations in imaging speed and the image distortions due to proximal scanning. Furthermore, scanning instabilities make OCT angiography (OCTA) methods difficult. Recently, we have developed an ultrahigh speed endoscopic OCT system enabling volumetric coregistered architectural and microvasculature imaging of the human gastrointestinal tract in vivo with the endoscopic OCT angiography (OCTA) technique. In this talk, we will discuss technical advances and clinical gastroenterology applications with the endoscopic OCT and OCTA techniques.