Mechanisms regulating the establishment of the glomerular endothelium and mesangium during glomerulogenesis are not understood. In this article, we discuss two different blood vessel growth processes: vasculogenesis and angiogenesis, with particular attention on how these processes might operate in the developing kidney. Results from metanephric organ cultures and interspecies grafts are also interpreted with an emphasis on generation of the renal microvasculature. Among the several growth factors identified in the metanephros, many (eg, fibroblast growth factor [FGF], vascular endothelial growth factor [VEGF], platelet-derived growth factor [PDGF], epidermal growth factor/transforming growth factor-alpha [EGF/TGF-alpha], hepatocyte growth factor/scatter factor [HGF/SF], and insulinlike growth factor [IGF]) have angiogenic properties, and these are discussed in relation to formation of the glomerulus. How extracellular matrices and proteases might be involved in vascularization are also considered.