Circadian variations in the carbohydrate metabolism of liver, blood glucose responses to food intake were examined in rats kept on a 12-hr light-dark cycle and fed during a restricted time of day 10:00-16:00) for 4weeks. Blood glucose levels from a hepatic vein were maintained regardless of food intake to a specific time of day. The muscle glycogen rhythm appears when rats are allowed to eat, and maximal level in found immediately after the feeding time. On the other hand, the hepatic glucose increased slowly to high level. Difference between blood glucose level in a portal vein and a hepatic vein showed daily changes corresponding to the rhythm of food intake in rats. When the blood glucose level in a portal vein was higher than that in a hepatic vein, the utility of the glucose in the postprandial was increased. In the contrary case, the gluconeogenesis was increased in the fasting time. The circadian rhythm of the insulin degradation in the liver showed increased in the fasting time, and decreased by feeding time. From these results, carbohydrate metabolism in the liver showed circadian rhythm that was related to the food intake. We concluded that the regular eating habits were important for health maintenance because of a feeding time was also important for the metabolic control of carbohydrate in the liver.