Bartter’s syndrome (OMIM #s: type 1, 60678; type 2, 241200; type 3, 607364; type 4a, 602522; type 4b, 613090; type 5, 300971) and Gitelman’s syndrome (OMIM # 263800) are autosomal recessive tubulopathies characterized by hypokalemia, metabolic alkalosis, activation of the renin–angiotensin–aldosterone system, high levels of angiotensin II (Ang II), but normo- or hypotension, and blunted Ang II cardiovascular effects. The gene discussed is REN; the disease is Gitelman syndrome.