To investigate the influence of the cholinergic nerves on the action of i.v. ethanol on interdigestive gastric acid, pancreatic enzyme, and bile acid output, seven healthy volunteers were studied. On each of 4 different days, they swallowed a multilumen intestinal tube system that allowed the measurement of intraluminal pressures and the collection of gastric and duodenal juice. The subjects received an i.v. infusion of either ethanol (600 mg/kg for 30 min followed by 3 mg/kg/min), atropine (5 mu/kg/h), a combination of both drugs, or NaCl. Whereas ethanol did not significantly influence motility, atropine induced motoric quiescence. Ethanol significantly (p less than 0.05) stimulated gastric acid output, by 55%, whereas atropine inhibited it by 91%. When ethanol and atropine were given together, gastric acid output was significantly higher than during atropine use alone. Both ethanol and atropine inhibited pancreatic amylase output--by 47% and by 82%, respectively. The degree of inhibition was 80% when ethanol and atropine were given simultaneously. Atropine but not ethanol significantly reduced bile acid output. The finding that atropine did not completely reverse the stimulating effect of i.v. ethanol on gastric acid secretion suggests that ethanol stimulates gastric acid secretion not only by a cholinergic but also by a noncholinergic mechanism. The observation that atropine did not reverse the inhibiting effect of ethanol suggests, but does not prove, that the effect of ethanol on the pancreas is predominantly mediated by cholinergic nerves.