The Cultrex® In Vitro Angiogenesis Assay Tube Formation Kit was developed for the evaluation of inducers and inhibitors of endothelial cell tube formation. During the course of the assay, endothelial cells are seeded on a thick gel of Basement Membrane Extract in the presence of angiogenesis modulating agents. If the medium is permissive to the angiogenic response, cells will self assemble into tube networks within hours; if there are inhibitors in the medium, tube network formation will be incomplete or nonexistent. Sulforaphane [1- isothiocyanato-(4R)- methylsulfinyl)-butane], found in broccoli and other cruciferous vegetables, is a naturally occurring cancer chemopreventive agent, and is provided as a control inhibitor to visualize this process. Endothelial cells may be fluorescently labeled using Calcein AM, and images captured using a microscope camera may be analyze to quantify the angiogenic response. Cultrex® In Vitro Angiogenesis Assay Kit provides a cost-effective method for investigation of prospective angiogenesis inhibitors in a 96 well plate format.