To assess the influence of the different intestinal segments on the plasma enteroglucagon level, three models of intestinal resection in the rat were studied (jejunal, ileal, 90%). The basal values for this peptide and those obtained after an infusion of intraduodenal glucose were compared. The results obtained in basal/post-glucose infusion were: 50% proximal (jejunum): 220/728 pg/ml; 50% distal (ileum): 10/233 pg/ml; and the middle 90%: 108/297 pg/ml. The glucose infusion produced a maximal response, permitting a better evaluation of the differences among the three resection models. The highest levels corresponded to the group in which the entire ileum was conserved.