SUMMARY 1. The ingestion of 50 g glucose by fasting subjects led to an increase of the concentration of adrenaline in venous plasma amounting to a mean value of 55% after 10 min. The effect was almost as marked 5 min after the glucose meal when the mean blood sugar level had only gone up by 3%. During the period 10–60 min after the glucose meal the concentration of adrenaline in the plasma gradually returned to its initial value. 2. The concentration of noradrenaline in the plasma was not significantly changed after a glucose meal. 3. The ingestion of 50 g fructose by fasting subjects was without effect on the concentration of adrenaline or noradrenaline in the plasma. 4. A glucose meal given 15 min before an intravenous injection of insulin slightly modified the effect of insulin on the concentration of adrenaline by delaying its initial fall and also its subsequent recovery. It is suggested that the rise in the level of adrenaline after a glucose meal is caused by a decrease in the hepatic utilization of the hormone.