Duodenal obstruction due to a gallstone from a cholecystoduodenal fistula (Bouveret's syndrome) is a rare complication of gallstone disease. Patients present gastric outlet occlusion with vomiting, abdominal distension and a state of dehydration. Plain film of the abdomen, ultrasonography and CT scans reveal pneumobilia and the obstructing gallstone. Endoscopy is essential for diagnosis and therapy, with a view to the possibility to relieving the occlusion. Endoscopy, however, cannot be used to treat the fistula and is often unsuccessful because of the very large size of the stone. Surgical therapy can be effective both for relieving the occlusion and for fistula treatment. The authors report a case of Bouveret's syndrome successfully treated surgically in an otherwise healthy patient. In critically ill patients, the primary goal of therapy is relief of the occlusion.