Gastrin heptadecapeptides (gastrins I and II which differ in the presence of sulfate on the tyrosine of the latter) have been purified and sequenced from several mammalian species including pig, dog, cat, sheep, cow, human and, more recently, rat. This report describes the purification of "little" gastrin from guinea pig (GP) antra. GP antra were defatted with acetone and the acetone cakes were extracted with 0.1M NH4HCO3. The extract was concentrated by adsorption to DE53 anion exchange cellulose and the peak eluates were fractionated on a Sephadex G50F column. The peptides were brought to final purity by 3 successive HPLC steps. The GP sequence compared to other species is shown: (formula: see text) Thus GP "little" gastrins I and II are hexadecapeptides due to a deletion of a glutamic acid in the region 6-9 from the N-terminus.