The effect of the intraperitoneal injection of 10(-5) M cholecystokinin-pancreozimin solution on the taste total impulse activity of the rat chorda tympani was studied. The taste responses to sodium chloride and sucrose increased within 5 min and responses to quinine increased within 30 sec after the peptide injection. Responses to citric acid solution did not augment significantly. The augmentation of the taste responses under peptide injection can be blocked by cutting the chorda tympani nerve or subepithelial administration of atropine solution.