Nitroglycerin increased the renal plasma flow and altered electrolyte excretion. Perhexiline, i. v., caused an increase in sodium, chloride and osmolar clearance without the changes in the renal plasma flow. An elevation of the tubular sodium rejection fraction probably contributed to the increased solute clearance. Isoproterenol caused retention of sodium, chloride potassium, and water without changing the renal plasma flow or the glomerular filtration rate. The tubular rejection fraction of sodium was decreased, indicating that isoproterenol was directly increasing the tubular reabsorption. The renal changes induced by isoproterenol were not altered by pretreatment with perhexiline.