Aim: To examine the contributions of insulin secretion, glucagon suppression, splanchnic and peripheral glucose metabolism, and delayed gastric emptying to the attenuation of postprandial hyperglycemia during intravenous exenatide administration. Experimental Design: 12 subjects with type 2 diabetes (44±2y, BMI=34±4kg/m², HbA_1c=7.5±1.5%) participated in 3 meal-tolerance tests performed with double tracer technique (i.v. 3-3H-glucose and oral 1-¹⁴C- glucose): (i) i.v. saline (CON); (ii) i.v. exenatide (EXE); (iii) i.v. exenatide plus glucagon (E+G) studies. Acetaminophen was given with the mixed meal (75g glucose, 25g fat, 20g protein) to monitor gastric emptying. Plasma glucose, insulin, glucagon, acetaminophen levels and glucose specific activities were measured for 6 hrs. Results: Post-meal hyperglycemia was markedly reduced (p<0.01) in EXE (138±16 mg/dl) and in E+G (165±12) compared to CON (206±15). Baseline plasma glucagon (~90 pg/ml) decreased by 20% to 73±4 in EXE (p<0.01) and was not different from CON in E+G (81±2). Endogenous glucose production was suppressed by exenatide (231±9 to 108±8 mg/min [54%] vs. 254±29 to189±27 mg/min [26%], p<0.001, EXE vs. CON) and partially reversed by glucagon replacement (247±15 to 173±18 mg/min [31%]). Oral glucose appearance was 39±4 g in CON vs. 23±6g in EXE, p<0.001 and 15±5g in E+G, p<0.01 vs. CON). The glucose retained within the splanchnic bed increased from ~36g in CON to ~52g in EXE and to ~60g in E+G (p<0.001 vs. CON). Acetaminophen (AUC) was reduced by ~80% in EXE vs. CON (p<0.01). Conclusion: Exenatide infusion attenuates postprandial hyperglycemia by decreasing endogenous glucose production (by ~50%) and by slowing gastric emptying.