The net productions of acetate and beta-hydroxybutyrate by the liver and portal-drained viscera were determined before and during insulin plus glucose infusions. Glucose was infused at rates to maintain euglycemia. During insulin infusion the net hepatic productions of beta-hydroxybutyrate and acetate were reduced to a greater extent than could be accounted for by a reduction in provision of free fatty acids to the liver. It is concluded that insulin has a direct anti-ketogenic effect on the ovine liver.