A stimulation of distal colonicmotoractivity was produced in anesthetized cats following intravenous administration of cholecystokinin. The contractileresponseelicited by cholecystokinin was not reduced following pretreatment with atropine. However, when animals were treated with agents which increased the net cholinergic input to the colon, a markedexaggerationof the subsequentcholecystokinin-inducedresponseoccurred. This cholinergically mediatedexaggerationwas produced following administration of the cholinergic agonist bethanechol, or after removal of tonic inhibitory systems mediated by prostaglandin or alpha-adrenergic input, whose blockade results in atropine-sensitive colonic stimulation. Cholecystokinin was also found to produce stimulation ofmotoractivity in the pylorus, jejunum, proximal colon and gallbladder. Cholinergically mediatedexaggerationof the cholecystokininresponsewas also present in the pylorus and proximal colon, but not gallbladder or jejunum. An inhibition of spontaneousmotoractivity was produced in the ileum or duodenum following cholecystokinin administration.