1. The contribution of the crop to gastric acid secretion was investigated in unanaesthetized chickens with a gastric fistula. 2. Basal secretion was enhanced by removal or distension of the crop and reduced by irrigating the crop with food suspension, acetylcholine, glycine or propyl alcohol as compared with phosphate buffer. 3. It was concluded that the crop is able to release stimulating and inhibiting impulses towards the glandular stomach. The stimulating impulses were elicited by mechanical, the inhibiting ones by chemical excitation.