The effect of intraventricular cholecystokinin-octapeptide (CCK-8) on blood glucose was evaluated. Intraventricular CCK-8 in rats produces hyperglycemia. The highest dose of CCK-8 (250 ng) increased plasma glucagon levels but at lower doses (2.5 and 25 ng) increases in glucose occurred without alteration in the glucagon levels. None of the doses of CCK-8 altered insulin levels. Using 14C-glucose tracer we showed that the hyperglycemia produced by CCK-8 was not due to alterations in glucose clearance.