Experimental studies on angiogenesis are clarifying many aspects of this important process and are leading to new approaches to use this information clinically. Histology of fixed tissues is a commonly used "gold standard" for assessing development of tumor vasculature during disease progression or changes in vasculature in response to genetic manipulation or therapy. However, histology provides only a static snapshot-in-time of vascular status, and can provide only limited information about vessel function or dynamics. Here we describe microscopy techniques and image processing approaches for using intravital video microscopy (IVVM) for the study of normal and tumor vascular morphology and function. IVVM provides powerful, high-resolution approaches for observing the vasculature in multiple organs or experimental animals. In addition to providing informative images, IVVM combined with video postprocessing and image analysis approaches can be used to extract valuable quantitative information from video images. This information includes morphological parameters such as vascular diameter, density, branching, and three-dimensional vascular geometry, as well as functional and physiological information such as the identification of vessels that are perfused with red blood cells (RBCs) or plasma, rate of RBC flow, and oxygen status of RBCs. An added strength of IVVM is the ability to provide longitudinal information, looking at changes in vascular morphology and function over time in individual animals. In this chapter, we describe methods and analytical approaches for using IVVM to study vascular morphology and dynamics.