Gastrointestinal motor abnormalities occur frequently in patients with diabetes mellitus. The gastrointestinal motor dysfunction in these patients has been associated with the presence of autonomic neuropathy. Recently, however, several studies have shown that the gastrointestinal motor responses to various stimuli are impaired during acute hyperglycemia in both healthy subjects and diabetic patients. It has been demonstrated that acute hyperglycemia impairs esophageal peristalsis, reduces the lower esophageal sphincter pressure, delays gastric emptying, slows intestinal transit, and reduces the gallbladder contraction in response to various stimuli in healthy subjects. In diabetic patients gastric emptying and gallbladder contraction have been shown to be impaired during hyperglycemia. With regard to the mechanisms of action, it has been suggested that hyperglycemia may affect gastrointestinal function through vagal-cholinergic inhibition, by alterations in serum osmolality, or perhaps by alterations in gastrointestinal hormone secretion.