In eight dogs, cellotomy, rubbing the small bowel, and exposing it to air suppressed the migrating bursts of action potentials and contractions that occur in the gastrointestinal tract during fasting and greatly slowed (one to three days) the gastrointestinal transit of 7-mm plastic spheres. The operation also caused a transient one-day increase in the concentration of epinephrine and a more prolonged five-day increase in the concentration and norepinephrine in arterial and venous plasma. Phentolamine mesylate and propranolol hydrochloride prevented the inhibition of the bursts of gastric action potentials brought about by operation, but these drugs did not alter the inhibition of the small intestinal action potentials or the speed of gastrointestinal transit of spheres.