To evaluate the effect of dietary carbohydrate content on postab- sorptive glucose metabolism, we quantified gluconeogenesis and gly- cogenolysis after 11 days of high carbohydrate (85% carbohydrate), control (44% carbohydrate), and very low carbohydrate (2% carbohy- drate) diets in six healthy men. Diets were eucaloric and provided 15% of energy as protein. Postabsorptive glucose production was measured by infusion of (6,6-2H2)glucose, and fractional gluconeogenesis was measured by ingestion of 2H2O. Postabsorptive glucose production rates were 13.0 6 0.7, 11.4 6 0.4, and 9.7 6 0.4 mmol/kgzmin after high carbohydrate, control, and very low carbohydrate diets, respectively (P , 0.001 among the three diets). Gluconeogenesis was about 14% higher after the very low carbohydrate diet (6.3 6 0.2 mmol/kgzmin; P 5 0.001) compared to the control diet, but was not different between the high carbohydrate and control diets (5.5 6 0.3 vs. 5.5 6 0.2 mmol/kgzmin). The rates of glycogenolysis were 7.5 6 0.5, 5.9 6 0.3, and 3.4 6 0.3 mmol/kgzmin, respectively (P , 0.001 among the three diets). We conclude that under eucaloric conditions in healthy subjects, dietary carbohydrate content affects the rate of postabsorptive glu- cose production mainly by modulation of glycogenolysis. In contrast, dietary carbohydrate content affects the postabsorptive rate of glu- coneogenesis minimally, as evidenced by only a slight increase in gluconeogenesis during severe carbohydrate restriction. (J Clin En- docrinol Metab 85: 1963-1967, 2000)