Background: Liddle's syndrome (or pseudoprimary aldosteronism) is a rare hereditary disease; only 18 cases have been reported since 1963. Its cause remains unclear, but one of its features is increased cell membrane permeability to ions., Patients and Methods: A diagnosis of Liddle's syndrome was made in 4 new cases, all female, two of them sisters (cases n0 3 and 4), at the ages of 2, 12, 5 and 4 years. The first manifestations were dehydratation with hypokalemia at 6 months (case n0 1), hypertension at 2 years (case n0 2), polydipsia with poor weight and height gain at 5 and 4 years of age (cases n0 3 and 4). At diagnosis, all the patients had severe hypertension, metabolic alkalosis, hypokalemia and hyperkaliuria, low plasma renin activity and serum aldosterone levels. Administration of antihypertensive agents was without effect, but the hypertension was reduced when triamterene and low-sodium diet were used. Hypercalciuria was observed in 2 cases and nephrocalcinosis in 2 (case n0 1 had both hypercalciuria and nephrocalcinosis). The 2 oldest patients (n0 3 and 4) developed progressive kidney failure, possibly due to reno-vascular disease secondary to hypertension. Patient n0 3 underwent kidney transplantation 18 years after the first symptoms of the disease. This resulted in the complete disappearance of her hypokalemia and hypertension. The red blood cell membrane permeability to K+ and Cl- was studied in all 4 cases before triamterene treatment. The passive permeability to K+ and (K+/Cl-) cotransport were both elevated. A second study, 3 years (cases n0 2 and 3) and 8 years (cases n0 1 and 4) later, of patients treated with triamterene showed low values for passive K+ permeability and (K+/Cl-)-cotransport., Conclusions: The 4 new cases of Liddle's syndrome had the classic features of the disease, except for hypercalciuria and nephrocalcinosis in 2 of them. The cell membrane permeability data are difficult to interpret. Hypokalemia and hypertension were immediately corrected after kidney transplantation in one case and remained so for 4 years, suggesting that this disease is tubular in origin.