Data on the embryonic derivation of metanephric endothelial cells are reviewed, paying particular attention to results obtained from anterior chamber and intrarenal grafts of embryonic kidneys. Most of the evidence supports an intrinsic origin of the endothelium, which probably differentiates from metanephric mesenchyme. The roles of several growth factor receptor/ligand systems are also discussed, with an emphasis on the VEGF receptors, Flk1 and neuropilin-1.