Summary We previously reported that GLP-1(7–36)amide had glucagonostatic action as well as insulinotropic action in the perfused rat pancreas. In this study, we examined the effect of GLP-1(7–36)amide on glucagon secretion and cAMP concentration in glucagon-secreting cell line, In-Rl-G9. GLP-1(7–36)amide (1nM) significantly suppressed glucagon secretion and decreased cAMP concentration in the cells. GLP-1(1–37) did not affect glucagon secretion. It is suggested that inhibitory effect of GLP-1(7–36)amide on glucagon secretion is at least partly mediated by adenylate cyclase system.