Renal function has been studied in normal human subjects over some hours after the administration of 250 mg cortisone acetate orally or of 100 mg cortisol intravenously. Increased output of potassium without elevation of plasma concentration, and retention of sodium, were observed regularly both in the course of and without a phosphate infusion. Glomerular filtration rate and renal plasma flow were sometimes markedly elevated, sometimes unaltered. When phosphate was infused in amounts sufficient to saturate tubular reabsorptive capacity, phosphate tubular maximum was often depressed by the hormones, but sometimes unaltered. At normal plasma concentrations the usual relationship between phosphate excretion and plasma concentration or filtered load was undisturbed.