Studies that address the cellular and molecular biology of renal organogenesis are relevant to our understanding of normal renal developmental mechanisms, developmental renal diseases, and the kidney's response to injury. Responses of the mature kidney to many injuries often involve cellular and molecular reparative processes that mimic development. This article will focus on recent data concerning regulators of renal differentiation; the roles of cell growth regulation, apoptosis, and intracellular signaling in kidney development; and specific mechanisms of renal epithelial, vascular, and interstitial development. Understanding the basic processes that occur in renal organogenesis provides insight into possible pathophysiological mechanisms operative in a wide range of renal diseases.