Duodenal ulcer is characterized by certain recurrence and occurs more often in men than in women. One can assume that functional changes, which are characterized by the seasonal nature and sex differences, play some role in its pathogenesis. There was a study of the duodenogastric reflux role in the pathogenesis of duodenal ulcer. It was revealed that duodenal reflux is provoked in about one half of patients sent for an endoscopic examination, less frequently--in spring and autumn, and least of all--in male patients with duodenal ulcer during seasons of the maximum frequency of duodenal ulcer exacerbations. The frequency of duodenogastric reflux provocation went down on days of geomagnetic storms. One could observe certain dependence between the extent and duration of reflux, on the one hand, and clinical registration of the disease, on the other hand.