Duodenal erosions may be classified as (1) Idiopathic erosions, a disease entity with a tendency to recur throughout a period of decades, and (2) Erosions as a stress reaction to various disorders. Massive bleeding may occur in both forms. It is of clinical interest that bleeding in a patient with duodenal erosions may not be from the duodenum but from concomitant stress haemorrhages in the upper part of the stomach. The natural history of duodenal erosions is reviewed, and 10 cases are analysed.