In experiments on conscious dogs i.v. administration of verapamil (3-4 mg/kg) reduced diuresis, natriuresis and glomerular filtration. After that the filtration returned to normal and diuresis and natriuresis increased. Following infusion into the renal artery verapamil enhanced diuresis and natriuresis due to inhibition of tubular reabsorption. In rats verapamil (5-10 mg/kg) increased diuresis and sodium excretion, but water diuresis is reduced at first.