Objective:To develop an experimental three-dimensional model by ECV304 cells(human umbilical vein endothelial cell line) for investigating the mechanisms of angiogenesis in vitro.Methods:ECV304 cells were seeded onto three-dimensional collagen gels made of rat-tail collagen.When the endothelial cells were cultured and grown to near confluence,treated with bFGF for 3 to 12 days,and then assessed with inverted phase contrast microscope.Results:The endothelial cells migrated into the gels,formed complex networks by cell cords at different levels through the bottom view,and sprouted capillary-like structures through the side view.Conclusion:ECV304 cells are capable of expressing some early events of angiogenesis in the three-dimensional collagen gels:proliferating,migrating and sprouting and so on.It should be useful for studying angiogenesis in vitro.