Circulating levels of the calcium-regulating hormones, calcitonin, calcitriol, and parathyroid hormone, were analyzed in relation to plasma renin activity in 10 persons with normal blood pressure and in 51 persons with essential hypertension. Calcitriol (p< 0.008) and parathyroid hormone (p< 0.01) levels were elevated in hypertensives with low renin activity, whereas calcitonin levels were higher in patients with high renin activity (p< 0.008), compared with normotensive controls and other hypertensive patients. Continuous relationships were observed between calcitriol levels and plasma renin activity in all patients (r= -0.65,p< 0.001) and between parathyroid hormone levels and urinary sodium excretion in hypertensive patients with low renin activity (r= -0.63,p< 0.01). Together, these results support a linkage between calcium metabolism and renin-sodium factors in essential hypertension. Calcium-regulating hormones and the renin-aldosterone system may coordinately mediate the blood pressure effects of differing dietary calcium and sodium intakes at the cellular level by altering cellular handling of monovalent and divalent ions.