Several N-acyl di-or tripeptides related to proglumide (PhCO-DL-Glu-NPr2) were prepared and their effects on gastric secretion were examined by intraperitoneal injection in rats. PhCOGlu (Phe-NH2)-NPr2, Z-Glu (Phe-NH2)-NPr2, PhCO-Glu (NPr2)-Phe-NH2 and PhCO-Asp-(Phe-NH2)-NPr2 inhibited gastric secretion, while PhCO-Glu (Asp-Phe-NH2)-NPr2 stimulated gastric secretion. Of these peptides, PhCO-Glu (Phe-NH2)-NPr2 showed the most potent inhibitory activity against gastric secretion, and was more potent than proglumide.