Glucagon had a marked enhancing effect (200-500%) on the renal excretion of I131, Na+, K+, Cl- and PO4[long dash]in both the anesthetized and conscious dog. Evidence is presented that these effects are not due to increased glomerular filtration, hyperglycemia, osmotic diuresis or a non-specific protein effect. The studies suggest that glucagon has a direct action on the kidney tubules.