(Case) 3X years old male: (Current medical history) In school days he had been aware of a subcutaneous mass in the left anterior chest and from the same period he often had severe headache but left it unattended. He was diagnosed with hypertension at the age of 20 years old and with giant left anterior thoracic arteriovenous fistula. He was operated but could not completely remove it. Then he has performed vascular embolization at five times. He was hospitalized for the sixth embolization in 202x due to increased arteriovenous fistula. A high blood pressure (178/97 mmHg) was observed at admission and the sixth embolization of the left thoracic shoulder lateral thoracic and internal thoracic artery was performed the day after hospitalization. After embolization he was discharged one week later. However the high blood pressure continued even after discharge and the headache did not improve so he was referred to our department. His father and mother and grandparents and brothers had high blood pressure. It may be suggesting familial and juvenile hypertension. Blood pressure of upper limb left 171/108 mmHg / right 178/112 mmHg (not significantly difference) ABI left 1.13 / right 1.10 and PWV left 2069 / right 1804 cm/s and arteriosclerosis was remarkable. CT imaging showed no adrenal enlargement but multiple kidney stones. Serum Ca and Mg levels were in the normal range and no high ARR84 (renin/aldosterone ratio) was observed. Ask-Mark syndrome was negative. He started taking amlodipine 5 mg for hypertension and then increased the dose and exchanged NifedipineCR 40 mg. After that carvedilol 10 mg was added and the blood pressure decreased to 120–130 / 70–80 mmHg and the control became good. Blood pressure showed a tendency to increase in eight months after the sixth embolization again and at the same time CT showed a slight increase in arteriovenous fistula. Conclusion: We experienced a case of juvenile-onset hypertension in which blood pressure could be controlled using three antihypertensive drugs in addition to the treatment of giant thoracic arteriovenous fistula embolization. The cause of juvenile onset and increased blood pressure was thought to be related to the effects of congenital battlement and longitudinal arteriovenous fistula which do not exhibit pulmonary circulation or circulatory system. Conventionally congenital battlement / longitudinal arteriovenous fistula has a mild left ventricular load and almost no increase in blood pressure has been reported. However it may be possible the left ventricular load became larger and caused hypertension because of the huge thoracic arteriovenous fistula.