Using 3 dogs with Pavlov pouches, the normal response to a meal was compared with the response as modified by exercise on a treadmill immediately after feeding. At least 10 exercise and 10 normal determinations of 8 hrs. each were made on each animal. Exercise of moderate or severe grade depressed the gastric secretion during the exercise period. Usually the gastric secretion during exercise did not rise above the basal level. Following the exercise there was in most instances a compensatory increase in the quantity of acid secreted. The rectal temp. during exercise rose 2-4[degree]C. Three possible explanations of the depression of secretion during exercise are offered: the rise in temp.-, a redistribution of blood, and a decrease in blood P.