Neovascularization plays a role in several pathological conditions, including tumor growth, arthritis, and choroidal neovascularization. Investigators from different fields can choose from several available angiogenesis assays according to their specific needs. This chapter describes an easy-to-perform assay that is based on the differentiation of endothelial cells and the formation of tube-like structures on an extracellular matrix, Matrigel. The assay can be used to screen compounds for angiogenic activity or to determine if it has an effect on angiogenesis, depending on the conditions chosen. It is a quick assay, easy to set up, and highly reproducible. It can be used to test one or two samples, or it can quickly be scaled up to screen hundreds of compounds. The flexibility that this assay provides makes it a good first choice to test if a compound or a series of compounds may play a role in angiogenesis.
