Recent advances in developmental nephrology have provided new evidence that retinoids, vitamin A and its active metabolites such as all-trans retinoic acid, profoundly influence renal organogenesis. Retinoids are acknowledged as potent nephron mass regulators. They regulate embryonic kidney patterning through control of Ret expression in a dose-dependent manner, which modulates ureteric bud branching morphogenesis. Analysis of retinoid availability and utilization provides additional evidence of retinoid involvement at sites of epithelial-mesenchymal interactions, suggesting a tight control of vitamin A homeostasis for proper renal morphogenesis and differentiation. This provides a rationale for the search for and identification of retinoid target genes.