Low renin hypertension comprises a spectrum of disorders ranging from primary aldosteronism to obvious disorders of other mineralocorticoids, as well as a variety of miscellaneous disorders. The largest group of patients with low renin hypertension have no clear abnormality in mineralocorticoid production. However, many lines of evidence suggest the critical role of volume excess in the pathogenesis of hypertension in these patients. More detailed physiological studies must be performed in order to totally understand the spectrum of pathophysiology in low renin hypertension. However, while such studies are in progress the evidence from the literature suggests that these patients must be treated and that in most of these patients diuretic administration, either spironolactone or the thiazide group of diuretics, is usually effective in achieving a reduction of blood pressure to normal.