A bioactive form of enteroglucagon has been isolated from porcine jejuno-ileum according to its glucagon-like effect in liver. Enzymatic digestion followed by HPLC, dansylation and partial sequence analysis strongly suggests that this peptide contains the glucagon molecule (1--29) elongated at the C-terminal end by the octapeptide Lys-Arg-Asn-Lys-Asn-Ile-Ala-COOH and possibly modified in the N-terminal region. A specific action of bioactive enteroglucagon, increase in cAMP, has been found in the acid-secreting fundic part of the rat stomach. The term "oxyntomodulin" is therefore proposed to describe this peptide.