Patients who are vol- & Na-depleted by vigorous diuretic therapy, dietary salt restriction, diarrhea or vomiting. Renovascular HTN, renal impairment & kidney transplantation, aortic or mitral stenosis or obstructive hypertrophic cardiomyopathy. Primary aldosteronism, hypertensive patients w/ type 2 DM & renal disease, hyperkalemia.