In dogs anesthetized with pento-barbital, partial clamping of abdominal aorta lowered the clearances of K and creatinine and that of K more than the creatinine. This effect also occurred in dogs previously given KC1 orally and then infused with KC1 during the clearances. Extraction of para-amino hippurate was not reduced by the hypotension. Hypotension had less effect in lowering K clearance when Na excretion was greater due to infusion of Na salts and in some instances clearance of K exceeded that of creatinine. However, hypotension continued to lower markedly the clearance of K.