Mutations in KCNQ1 and KCNE1, the alpha- and beta-subunits of the I(KS) K+ channel, produce the cardiac long QT (LQT) syndrome. These subunits are expressed in heart and inner ear, but also in epithelial tissues such as kidney or intestine where their functional roles have remained elusive. Recent work has shown that KCNE1-deficient mice display chronic hypokalemia and hyperaldosteronism. These results have significant implications for human congenital LQT syndromes because hypokalemia increases the risk of ventricular arrhythmia and cardiac sudden death.