A glycogen storage disease(GSD) type I is a metabolic disease caused by a deficiency in one of the components of the glucose-6-phosphatase(G-6-Pase) system. This disorder results in hypoglycemia, hepatomegaly, lactic acidemia, hyperlipidemia, and hyperuricemia. Common long(-)term complications include growth retardation, gout, hepatic adenomas, osteoporosis and renal disease. However the cardiovascular system is rarely involved, and only six cases of pulmonary hypertension associated with GSD I have been reported in the literature. We experienced a case of pulmonary hypertension with type I GSD. A 31-year-old man, who had discovered type I GSD and received portocaval shunt operation 22 years ago, was admitted to the hospital with the chief complaint of dyspnea. Echocardiographic examination and cardiac catheterization revealed severe pulmonary hypertension. Nitric oxide and oral prostacycline derivative(beraprost) were tried without acute favorable response. After one year with beraprost, dyspnea, exercise capacity and hemodynamic parameters were improved. We report this case with a review of the literature.