The aim of this study was to investigate the effects of catecholamines on motility of stomach and intestine in chronic experiments on dogs with fistulas in stomach and duodenum. The contractions of stomach and duodenum were registered by a balloon method. It was established that i.v. adrenaline and noradrenaline injections in dogs with intact vagi inhibited food-induced motility in stomach and duodenum and did not produce contractions in the empty and quiescent gastrointestinal tract. Beta-adrenoagonist isoprenaline on the contrary produced stomach and duodenum contractions in fed dogs during the quiescent period. In fed dogs isoprenaline caused a 3-phasic reaction: a phase of primary short-term suppression of stomach and duodenum motility, a phase of motility increase and a phase of secondary suppression of stomach and duodenum motility. The contractions evoked by isoprenaline in the stomach resemble in amplitude and shape, periodical activities which are typical for fasting dogs. Vagotomy intensified isoprenaline motor effects in hungry and fed dogs and eliminated the phase of primary suppression in fed dogs. The isoprenaline effects were blocked by propranolol, but not by phentolamine. They were decreased more effectively in the stomach by atropine and by hexomethonium in the duodenum.