Changes in plasma active and inactive renin concentrations (ARC and IRC) were measured in 10 patients with primary aldosteronism (PA) due to adrenal adenomas. Before the resection of adrenal adenomas, venous blood samples were taken at supine resting state, after 1-hour standing and 30 min. after furosemide injection and these samplings were repeated after surgical treatment. Plasma inactive renin was measured after activation with trypsin. Before the treatment ARC and IRC did not change by standing or furosemide. After the treatment, however, ARC was increased clearly by standing or furosemide, and IRC was also increased by furosemide injection. Both ARC and IRC at supine resting state were increased after the surgery. When the renin-angiotensin system is suppressed chronically by the over-produced aldosterone in patients with PA, not only active but also inactive renin secretions are suppressed, and fail to respond to orthostasis or furosemide. The secretion of IR could be stimulated after the removal of aldosteronoma.