A 19-year-old man with an adrenal tumor associated with hypertension is herein described. The plasma renin activity (PRA) was markedly elevated and the plasma aldosterone level was also increased. The catecholamine level was within the normal range and the glucagone-regitine test was negative. An angiogram revealed the left renal artery to have no stenotic segments, but instead was curved caudally. Magnetic resonance imaging showed a tumor measuring about 8 cm in diameter to be clearly recognized from the left kidney. The blood pressure did not drop when a calcium-channel blocker was used, but was gradually stabilized with the angiotensin converting enzyme (ACE) antagonist. The adrenal tumor was then removed surgically. Normal adrenal tissue was scarcely recognized to the left of the tumor. After surgery, the PRA decreased and blood pressure stabilized rapidly without the ACE antagonist. The possibility of massive renal renin secretion due to suppression by the adrenal tumor was excluded by a method using an antibody to purified human renin.