Inhibitors and stimulators of endothelial cell growth are essential for the coordination of blood vessel formation during organ growth and development. In the adult kidney, one of the major inhibitors of angiogenesis is pigment-epithelium-derived factor (PEDF). We have analyzed the expression and distribution of PEDF during various stages of renal development and aging with particular emphasis on the formation of functional glomeruli. We show that PEDF gene expression and protein levels in the kidney significantly increase with age. We have detected PEDF in the mesenchyme and endothelial cells at all developmental stages studied, in all regions of the nephrogenic zone in which the formation of new blood vessels is associated with the development of nephrons and collecting ducts, and in mature podocytes in the adult kidney. Our results are the first to suggest that PEDF is important in early renal postnatal development, that it could be relevant to the maturation of glomerular function and the filtration barrier formed by these cells, and that it may serve as an anti-angiogenic modulator during kidney development.