Argininosuccinic aciduria (ASA) is an inborn error of ureagenesis which if untreated leads to hyperammonemia, accumulation of argininosuccinic acid and arginine depletion. The presence of high blood pressure in patients with ASA has been reported so far as transient in one newborn. We describe the first two patients, one child and one young adult, with ASA and persistent systemic hypertension. Extensive evaluation of both patients excluded secondary causes of systemic hypertension. The intriguing link between nitric oxide (NO) production and hypertension lead us to hypothesize that the deficiency of endogenously synthesized arginine caused by ASL deficiency is responsible for the increased blood pressure.