Chloride channels are expressed along the entire mammalian nephron. They participate in transepithelial chloride transport, cell volume regulation and acidification of intracellular vesicles. Some chloride channels are constitutively active and others are regulated by either second messengers such as cAMP or Ca(++) or secondary to changes in membrane potential. The molecular identities of a number of chloride channels within the kidney are still unknown. Abnormalities in chloride channel expression and function in the kidney can cause a range of disorders such as autosomal recessive Dent's disease, Bartter's syndrome, renal tubular acidosis and diabetes insipidus. The purpose of this review is to give an overview of the chloride channels in the kidney and to focus on the function of renal chloride channels as revealed by diseases associated with channel dysfunction.