Liddle's syndrome is a rare form of hereditary hypertension caused by mutations of the epithelial sodium (Na(+)) channel (ENaC). Analysis of the diseased pedigrees indicates an autosomal dominant inheritance, and the identified mutations are heterozygotes of gain-of-function mutations. However, sporadic cases of Liddle's syndrome have been reported in the literature, including one recently reported case caused by a de novo mutation of ENaC. We identified two patients with Liddle's syndrome who did not have family histories of hypertension. Sequence analysis showed a mutation in each case (P616L in betaENaC and W576X in gammaENaC), both confirmed to be de novo mutations. These data indicate that Liddle's syndrome should be considered even in patients without a family history of hypertension.