The inhibition of angiogenesis represents a major step toward a more selective and better-tolerated therapy of cancer. An alternative way to take advantage of a tumor's absolute dependence on a functional neovasculature is illustrated by the strategy of "antibody-based vascular tumor targeting." This technology aims at the selective delivery of bioactive molecules to the tumor site by their conjugation to a carrier antibody reactive with a tumor-associated vascular antigen. A number of high-affinity monoclonal antibodies are nowadays available which have demonstrated a remarkable ability to selectively localize to the tumor vasculature. Indeed, some of them have already progressed from preclinical animal experiments to clinical studies in patients with cancer, acting as vehicles for the site-specific pharmacodelivery of proinflammatory cytokines or radionuclides.In this chapter, we present a selection of well-characterized markers of angiogenesis which have proven to be suitable targets for antibody-based vascular targeting approaches. Furthermore, different transcriptomic and proteomic methodologies for the discovery of novel vascular tumor markers are described. In the last two sections, we focus on the discussion of antibody-based vascular tumor targeting strategies for imaging and therapy applications in oncology.