Abstract Alcohol generates a large caloric yield without supplying any essential nutrients; alcoholics may thus maintain body weight while suffering from malnutrition. In addition, diarrhea is a common complaint of both acute and chronic alcoholics. Here, we review the effects of alcohol on gastrointestinal morphology, function, its nervous system and motility. Acute morphological changes such as erosions, inflammatory cell infiltrations and microvascular changes are seen in the stomach and small intestine in acute alcoholics. In addition, atrophic gastritis, reduced villous height and decreased mucosal surface area of the small intestine have been described in chronic alcoholics. Acute administration of alcohol inhibits absorption of nutrients and fluids, and can stimulate secretion of water and electrolytes. Bacterial overgrowth in the proximal small intestine and decreased pancreatic secretions have been also described in chronic alcoholics. The well-known deleterious effects of alcohol on the central nervous system raise the possibility of similar acute and chronic effects of the enteric nervous system. Such effects could alter motility and transit. Indeed, esophageal dysmotility and delayed gastric emptying have been observed with high concentrations of alcohol in experimental studies and in chronic alcoholics. Small bowel motility and transit may be abnormal in both acute and chronic alcoholics, and colonic propulsive motility is increased after acute administration of alcohol. Any, or all, of these changes in gastrointestinal functions may contribute to diarrhea in acute binge drinkers and chronic alcoholics. Unfortunately, there is a lack of systematic studies of the pathophysiology of alcohol abuse, and an integrating concept of the diarrhea of alcoholics is still not possible.