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Objective: Despite the reduced number of β-cells, glucose metabolism often improves after major pancreatic resection. To investigate the postoperative pancreatic β-cell function and hormonal responses of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) using the two different types of pancreatectomy; pancreatoduodenectomy (PD) and distal pancreatectomy (DP).Summary Background Data: Incretins have been recently identified to have important roles in the regulation of the pancreatic β-cell function by stimulating insulin secretion, and become a topic in the field of the treatment of diabetes mellitus. Roles of incretins after pancreatectomy which causes the decreased number of β-cells has not been well documented. Methods: Oral glucose tolerance tests were performed in 34 patients who underwent pancreatectomy (20 PD and 14 DP) before, 1 month and 6 months after operation. There were 14 patients with malignant diseases (70%) in 20 patients undergoing PD and 5 (36%) in 14 DP. The changes in the serum glucose and insulin concentrations, homeostasis model assessment of insulin resistance (HOMA-IR) and homeostasis model assessment of β-cell function (HOMA-β) were analyzed. The plasma concentrations of GLP-1 and GIP were also measured.Results: Plasma GLP-1 concentration 1 month after DP transiently increased (P<0.05), while such a change was not observed in PD group. On the other hand, GIP concentrations after PD continued to be lower compared with the preoperative values (P<0.01), although there was no significant change in DP group. Postoperative glucose concentrations were significantly lower than preoperative values in PD, while those values were the same in DP. Postoperative insulin concentrations were significantly lower than preoperative values in both PD and DP groups. Although HOMA-IR improved transiently 1 month after PD (P<0.05), such improvement was not observed after DP. The value of HOMA-β after PD was significantly lower than that before operation (P<0.05), while that of DP was not significantly different from the preoperative value. Conclusions: The glucose metabolism after PD was different from that after DP in terms of postoperative β-cell function and hormonal responses of GLP-1 and GIP. Incretins seem to have roles to regulate the postoperative glucose metabolism after pancreatectomy.