Human renal dysplasia is a collection of disorders in which kidneys begin to form but then fail to differentiate into normal nephrons and collecting ducts. Dysplasia is the principal cause of childhood end-stage renal failure. Two main theories have been considered in its pathogenesis: A primary failure of ureteric bud activity and a disruption produced by fetal urinary flow impairment. Recent studies have documented deregulation of gene expression in human dysplasia, correlating with perturbed cell turnover and maturation. Mutations of nephrogenesis genes have been defined in multiorgan dysmorphic disorders in which renal dysplasia can feature, including Fraser, renal cysts and diabetes, and Kallmann syndromes. Here, it is possible to begin to understand the normal nephrogenic function of the wild-type proteins and understand how mutations might cause aberrant organogenesis.