The effects on renal function of an intravenous infusion of calcium gluconate at subpressor doses have been investigated in a group of seven normotensive male volunteers. In the absence of changes in blood pressure, the calcium gluconate induced a significant increase in renal plasma flow and the glomerular filtration rate (P less than 0.01) with a significant fall in the filtration fraction (P less than 0.01). Both diuresis and natriuresis increased significantly (P less than 0.01), plasma renin activity fell (P less than 0.01) and the urinary excretion of 6-keto prostaglandin F1 alpha (PGF1 alpha) and prostaglandin E2 (PGE2) increased (P less than 0.01). These results indicate that calcium infusion at subpressor doses has renal vasodilating, diuretic and natriuretic properties that appear to be facilitated by an increase in the renal production of vasodilatory and natriuretic prostaglandins.