The incidence of severe duodenal anomalies (MD) has been investigated in 458 patients submitted to barium meal examination and in 176 subjects comprising various clinical subgroups. The incidence of MD in patients submitted to barium meal examination was 11.6%. The incidence of MD in 25 normals was 4%, which was not significantly different from the incidence (10%) of MD in patients with gastroesophageal reflux symptoms. Compared with in normals, MD occurred with a significantly higher incidence in 45 patients with X-ray-negative dyspepsia (24%), in 36 patients with the irritable bowel syndrome (44%), and in 37 patients with asthma (38%). It is concluded that demonstration of MD in a patient is only indicative of a possible disorder.