Familial Bartter's syndrome is considered to be an autosomal recessive disease. Because an activation of the renin-angiotensin system is a characteristic feature of this disease, we evaluated a possible changes in renin gene. However, we could not detected any molecular abnormalities of renin gene, i.e. gene duplication, insertion/deletion polymorphism, nor peculiar frequencies of renin RFLPs. For further study, we must collect large numbers of affected families of this disease, and examine more various candidate genes including Cl(-)-transport proteins.