Duodenal diverticulum is a pouch like protrusion of the mucous membrane through a weak area or defect of the muscous layer of the duodenal wall. 206 cases of the duodenal diverticula out of consecutive 4030 cases on upper G-I series during the period from Feb. 1977 to Aug. 1978 in the Department of Radiology, College of Medicine, Hanyang University were studied. The results were as follows: 1. Overall incidence of duodenal diverticula was 5.1 per-cent (5.0 per-cent in male, and 5.3 per-cent in female). 2. The incidence of duodenal diverticula were1.4 per-cent in the age group below 19, 1.4 per-cent in the second decade, 0.8 per-cent in the third decade, 2.4 per-cent in the fourth decade, 5.3 per-cent in the fifth decade, 10.2 per cent in the sixth decade, 9.2 per-cent in the seventh decade, and 17.0 per cent in the age group over 70. The incidence of duodenal diverticula is higher in the older individuals. 3. Male was more frequently affected in the age group below 40, but mor in females in the age group over 40. 4. 76.3 per-cent of duodenal diverticula were found in the concave side of the second portion of the duodenum. 5. Multiplicity of duodenal diverticula was 5.8 per-cent of cases. Triple duodenal diverticula were found in 1 case. 6. The size of duodenal diverticula was variable from 3 to 70 mm in diameter. More than half of duodenal diverticula were smaller than 9 mm in diameter. Large diverticula of more than 30 mm in diameter were 13.6 per-cent of cases. The sizes of the duodenal diverticula were relatively large in older age group.