Isolated mucosal preparations from the stomach are generally obtained by removing the external muscle layers, leaving intact the muscularis mucosae. By carefully dissecting off the muscularis mucosa, we have obtained "epithelial" preparations from the canine stomach. Such preparations responded to secretagogues, histamine, pentagastrin, and a cholinergic agonist (cis-2-methyl 4-dimethylaminomethyl 1,3-dioxolane methiodide). Epithelial preparations were, in general, more sensitive than mucosal preparations. Of the three secretagogues tested, histamine was the most consistent stimulant, with well-sustained responses being noted. Responses to the other agonists were more variable. Pentagastrin produced brief but explosive increases in acid output.