Angiogenesis has been defined as sprouting of blood vessels from pre-existing vascular structures. Risau and co-workers defined the term vasculogenesis while studying the formation of new blood vessels in embryoid bodies. This process is characterized by the recruitment of endothelial progenitor cells (EPC) to sites of new vessel formation with subsequent differentiation of EPC into mature endothelial cells, extensively proliferating in situ. Data from recent years provided evidence that EPC also exist in the adult and contribute to new vessel formation, a process called post-natal vasculogenesis. The existence of EPC has been convincingly shown in both, animals and humans. They represent a perfect cellular progenitor cell population for the ex vivo generation of EC, which in turn serve as cellular source for therapeutic vasculogenesis or tumor targeting. This review provides an overview on this hot topic of cellular-based therapeutic concepts and the therapeutic potential of ex vivo generated EPC.