Adipokinetic hormones II from corpora cardiaca of the locusts Schistocerca gregaria and Locusta migratoria, respectively, have been isolated and their primary structures elucidated. Both octapeptides are N-terminally blocked by a 5-oxoproline (pyroglutamate) residue and had to be cleaved by 5-oxoprolyl-peptidase to make them available for the Edman degradation method carried out with a gas-phase sequencer. The C-termini are blocked as both peptides are not cleaved by carboxypeptidase A; the presence of C-terminal amide groups is very likely. AKHII (S. gregaria) Glu-Leu-Asn-Phe-Ser-Thr-Gly-Trp-NH2 AKHII (L. migratoria) Glu-Leu-Asn-Phe-Ser-Ala-Gly-Trp-NH2.