A prospective, double-blind clinical study of the double-contrast upper gastrointestinal examination involving 240 patients was performed using glucagon in doses from 0.025 to 0.125 mg, in 0.025 mg increments. Although motility was diminished, neither gastric distension or coating was improved with the use of glucagon. However, duodenal distension and coating were markedly enhanced. The response of the pylorus was individualistic. The pylorus remained patent in most patients, and glucagon would not prevent barium spillage in the duodenum. However, in those patients with a "competent" pylorus, increasing glucagon doses produced a delay in gastric emptying. Several other variables, including weight, age, and gender, were studied and were not believed to be of clinical significance. Spontaneous gastroesophageal reflux was also increased with the use of glucagon. Glucagon mainly enhanced duodenal visualization but had no beneficial effect on the stomach or pylorus. Absolute dose is the most important factor, and all observable changes can be seen once a certain threshold dose (0.05 mg) is reached.