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Uromodulin is the most abundant protein excreted in the urine under physiological conditions. It is exclusively expressed in the kidney by epithelial cells lining the thick ascending limb of Henles loop. It is mainly localized at the apical plasma membrane of tubular cells and released through a proteolytic cleavage. Although its function is still elusive it is proposed to have a protective role against urinary tract infection and kidney stone formation, in ion transport and in kidney innate immunity. Mutations in the gene UMOD encoding uromodulin lead to rare autosomal dominant diseases, collectively referred to as uromodulin-associated kidney disease, that are characterized by progressive tubulo-interstitial damage, impaired urinary concentrating ability, hyperuricemia, and progressive renal failure. Recently, genome-wide association studies identified uromodulin as a risk factor for chronic kidney disease and hypertension. Risk variants in the UMOD gene are common in all studied populations and are associated with higher expression and urinary level of the protein.