Mendelian forms of hypertension are rare genetic disorders that cause severe hypertension. This review will explore the recently identified molecular mechanisms and pathogenesis of genetic disorders that cause hypertension in children.Hypertension is now believed to be a polygenic disorder resulting from the interaction of multiple genes and the environment. A few forms of severe hypertension have been linked to single genes. The genes responsible for these disorders have all been cloned and all participate in pathways involved in heightened renal sodium reabsorption. The increased sodium reabsorption arises in the distal nephron and leads to volume expansion and hypertension.Investigating forms of monogenic hypertension has advanced the understanding of sodium transport and volume control by the kidney. Future studies will identify novel genes, pathways and treatment targets important in the fight against primary hypertension.